Poland's foreign policy if it breaks away from Russia after a revolution in a no-WWI scenario

I concur in these circumstances continued independence of Poland is only feasible if Russia stays weakened by ongoing instability or Germany steps up to be Poland's ally and protector. If the Polish leaders were talented enough to accomplish a successful breakaway from Russia in the first place and a resurgent Russia later stabilizes enough to be a serious threat for Poland, I assume they would also be pragmatic enough to put their potential territorial claims on Austrian and German land deep into the freezer and ally with the CP. At most they would very politely lobby for German and Austrian Poles getting cultural and/or administrative autonomy.

As it concerns the military disadvantages of a CP alliance for Poland, I do not assume they would actually be that great, since in practice the Eastern front portion of the Great War would be largely fought on Baltic, Belarusian, and Ukrainian land rather than Polish one, unless the Polish army proves to be even more incompetent than all the other WWI belligerants or the Russian one substantially better than OTL. Even if the German war plan is the OTL one, either Plan Schliffen succeeds and then the CP walz their way into victory or (more likely) it fails and the Germans quickly turn to throw the bulk of their military power on the Eastern front before the Russian army can advance much deep into eastern Poland and Galicia. In practice the CP-cum-Poland would start WWI on the Eastern front someplace close to the eastern bank of the Vistula or the Bug (depending on which border the Poles were able to win from Russia in their war of independence) and steadily fight their way eastward until Russia collapses (again) into revolution, which would be a substantial strategic gain for the CP at large and not much of a serious burden for Poland (not more so than for the other WWI belligerants, anyway). Certainly this would mean the timetable of Russia's collapse is substantially accelerated, say by a year to year and half or so. This would almost surely guarantee a CP victory.

An interesting question in this scenario is whether the strategic shift in the balance of power the CP-Poland alliance would cause is enough to make Italy assume the CP are likely going to win and stay loyal to the Triple Alliance out of a wish to grab Nice, Savoy, Corsica, and Tunisia even if A-H turns out to be the usual tight-fisted, off-putting dicks that would not concede anything ever to compensate their allies despite pacts to the contrary. I think it would be quite possible and even likely, making a CP victory even quicker and easier. Of course, the Italians and the Poles would fight WWI to grab their own booties from France and Russia and in the secret hope the war effort causes postwar A-H to collapse, allowing them to pick their own chosen pieces. More or less the same point applies for Romania, which has good chances to assume the CP are going to win and join them to grab Bessarabia. ITTL it is exceedingly likely the expanded CP coalition would see victory on the horizon well before Germany ever feels tempted to use USW in earnest, which means the USA stays a true neutral and the Entente is toast.

Also, this is a radical idea, but I might as well propose it here: Could an independent Poland try joining Austria-Hungary? After all, this would allow it to reunify with some of its long-lost brethren and also make it much more secure since it would now be a part of a Great Power. Unifying with Germany makes no sense since the Germans will decisively outnumber the Poles, and reunifying with Russia would obviously be unacceptable to the Poles due to the fact that Russians will massively outnumber Poles. If continued independence for Poland doesn't look that attractive, might Poland desire to unify with Austria-Hungary?

For the record, if Poland is added to the Austrian part of Austria-Hungary, then it's possible that Poles would actually make up a majority or at the very least a plurality of the total population in Austria--something which should give the Poles a lot of political power. Of course, the downside in joining Austria-Hungary is that Poland would likely have to forever say goodbye to its territorial claims in the German Empire.

1. I don't see why exactly Germany would have to break from Austria-Hungary in the event that Austria-Hungary annexes Congress Poland. After all, as long as Austria-Hungary doesn't make any claims on German territory, Germany and Austria-Hungary can still be allies against Russia.

2. Yeah, as I wrote above, Russia would have already lost most of its Polish-heavy territories while Germany and Austria-Hungary would still have a lot of Polish-heavy territories in Galicia, Upper Silesia, Posen, the Polish Corridor, and Masuria. Thus, you appear to be very much correct that Poland would likely ally with Russia if Russia didn't pose a renewed threat to Polish independence. Frankly, I would think that Russia's leadership would be smart enough to realize that threatening Poland isn't going to be very productive and will thus instead aim to cooperate with Poland. After all, it's much better to have Poland as an ally than to have it be a part of your country and be a constant pain-in-the-butt for you.

Also, as I previously wrote, Poland is going to be aware that there is a very serious risk that it will be the battlefield in any future conflict between Russia and Germany + Austria-Hungary. However, if Poland wants to expand, this is the only way for it to do so.