Successful Weimar Germany

  Very true except that unfortunately many have been drawn to the bigots and fanatics because rulers and in some cases those who replaced them, offered no better [as it appeared at the time] alternative.

  Good question.  I suspect not a lot in foreign affairs terms. 

  Its probably going to be continually isolated as it wouldn't have either the de-facto alliance with the Nazis getting it a chunk of eastern Europe and then the one with the allies which got it even more.  It might try going for the Baltic states at some point or Finland but going any further is likely to result in a pretty comprehensive European alliance against it.  Possibly with no clear threat from Europe Stalin might follow up Zhukov's successes against the Japanese and the Soviet support of the KMT to really plough into Japan.

  What it might do a bit later is be more active in anti-colonial campaigns as European powers are probably going to seek to hang onto their colonies longer without WWII.  Or possibly sink into further rounds of repression and periodic purges and slaughter.

  Possibly although Stalin was supporting the KMT initially as the best counter against the Japanese, even after the KMT turned on the local communists.  However might switch after the defeat of Japan as Stalin might find the KMT too independent.  However doubt it would be a surviving Wiemar Germany supporting the KMT as it had relatively little interests in E Asia.  More likely Britain or the US because of their interests in China and opposition to the communists.

1 - Then we may assume it happens ITTL. I am confident in these circumstances friendly relations and close economic ties may soon resume between Czechoslovakia and Germany. It is questionable whether the Czechoslovak state is going to survive with a federal reform or experience a breakup like OTL.

2 - Well, it may well happen ITTL the Poles see the writing on the wall and accept to make the minimum necessary concessions to settle the crisis for good. It's good enough for me and perfectly fitting the circumstances of the scenario. I only gave preference to the crisis being settled through a brief German-Polish war with a Soviet intervention because it seemed better for story reasons and the overall picture (i.e. a more threatening USSR may give the Europen powers greater reason to reconciliate and cooperate). And yes, the 1807 German-Polish border seems much better from my geopolitical PoV, and I'm undecided about the best Polish-Soviet border.

3 - Really, no. I may have avoided going into detailed hard numbers about the Franco-German balance of forces since I'm not confident I have the appropriate expertise, but broadly speaking something basically equivalent to military parity between France and Germany seems the best solution to make both powers be and feel reasonably secure about their security on their shared border, with all the fortifications they may wish to have on their side. I have no particular wish or urge for 'French and other western forces are strictly limited but Germany can maintain much larger forces French and other western forces are strictly limited but Germany can maintain much larger forces, which in the event it turns rogue again could very quickly be moved westwards again' to happen, I don't think a democratic Germany would seek that nor it would be possible to make interwar France accept it.

My main concern besides restoring an equal military standing between the two powers is to ensure the Western European powers keep the military resources prepared to counter a possible Soviet attack in Eastern Europe and stop it before it reaches Berlin and Venice. Since by the 1940s the build-up of the Soviet military-industrial complex shall make the Red Army so powerful the Eastern European armies on their own would only be speed bump to the Soviets. Once the USSR grows into its WWII self and the flaws that caused the Winter War fiasco get ironed out, only a well-armed, hopefully NATO-style European alliance can hold back a possible Stalinist rampage without too much damage. So I'd say in addition to basic military parity between the European powers, what is needed is the sum of them to have enough military resources ready to mobilize and enable effective deployment, defence, and counterattack in a possible conflict with the USSR in Eastern Europe and the Middle East before the theater gets overrun. Nothing more, nothing less, to be shared among alliance members according to their respective resources and an equitable burden-sharing.

4 - Another really, no. The mindset you advocate here to argue these minor concessions to Italy would cause widespread international alienation and instability was only shared by small activist left-wing fringe minorities if any in the 1930s. Such a mindset would only get a chance to become politically mainstream and dominant in Western public opinion because of the huge backlash from events (Nazism and its misdeeds) that did not happen ITTL and never will. To project the values of post-WWII liberalism, 21st century hard-left progressivism, and identity-politics activism on the distant past and make summary judgements or expectations on its events and actors because of this is a bad presentist mistake, albeit one social-justice bullies and fanatics are unfortunately all too often happy to make in order to tar and feather past luminaries when they fail to meet PC/SJW impossible standards. If anything, TTL circumstances (no Nazism but still Stalinism) are quite likely to adjust the mainstream of Western public opinion so that liberalism shall remain rather more moderate and pragmatic as well as right-wing ad realpolitick mindsets much more respectable and influential for the foreseeable future.

It is quite unlikely fascist Italy on its own without the enablement and toxic influence of Nazism would be willing and able to start a WWII-style rogue rampage of its own, with or without these minor concessions. But to make a great power like Italy content and cooperative seems rather more valuable for international stability than to sacrifice the interest of a couple insignificant small states or peoples that in the 1930s would be burdened with the imperialist yoke anyway. These concessions had seemed perfectly reasonable to the Entente powers just a couple decades ago, and if anything, TTL events are going to make reasonable amounts of appeasement look like the wise choice and intransigent opposition to them lunatic belligerance.

Quite possible. The precedent of the Sudetenland Germans may well persuade the Slovaks to seek a similar course even if Weimar Germany is not especially committed to support them, and if the Czechs overreact a civil war instead of a peaceful breakup or a federal reform may well happen. Such a conflict is going to cause some inevitable meddling by the Hungarians, Soviets, and Germans.

Much the same way but even more so, I expect interwar Yugoslavia most likely shall eventually collapse even without aggression or destabilization by the Axis powers. Especially since by the early 1930s the Serbian ruling elites had already sought the stopgap course of setting up a centralist dictatorship dominated by them, which in the long term is only going to exacerbate the ethnic tensions it tried to suppress, and the Serbs were not strong enough to keep the other nationalities down all the time, as history showed. If a Yugoslav collapse or civil war happens, then the neighbor powers with claims on its territory are inevitably going to intervene in some way.

It is quite unlikely it would happen since depending on the PoD that enables the success of Weimar Germany a democratic Anschluss may well occur before Dollfuss would take power in the first place, such as it happens in my scenario where the PoD is in 1930-31 and includes the success of the 1931 union attempt while Dollfuss took power in 1934 a few months before his assassination. Even if Dollfuss would take power for a while he would face the combined mobilized opposition of democratic parties and Pan-German nationalists to his rule. His power base would be far too limited and in all likelihood he would fall from power before too long or even fail to take over in the first place. His life may be spared ITTL but that's it. IOTL the Nazis took his life but otherwise bungled the coup against his regime spectacularly, otherwise the Anschluss would have easily taken place several years earlier than OTL, even if they needed to bargain with Mussolini to ensure his compliance.   

Unless the Germans bungle their act spectacularly, by seeking compensations, no doubt. Mussolini reacted with the threat of military force in 1934 since the Nazis bungled their coup but 1938 events indicate he could be won over to acquiescence about Anschluss fairly easily. Suitable means include German support to Italian ambitions in Ethiopia and the Balkans, an analogue of the 1939 agreement to transfer South Tyrol Germans to Germany, or even establishment of a bilateral demilitarized zone on the German-Italian border. Weimar Germany had zero interest in an independent Ethiopia or Albania or a non-Italian Dalmatia, and might actually benefit in a geopolitical sense from the breakup of Yugoslavia, so to support fascist Italy in the fulfillment of its ambitions about these areas would cost or risk the Germans very little. Not to mention Yugoslavia was actually rather likely to collapse on its own.