How does a surviving Vichy France handle decolonization?

  Well they would almost certainly take a harder line, especially in places near to Algeria and probably in Syria and W Africa.  They might not lose FIC in this scenario as Britain making peace this early could negate the full occupation of it by Japan, and/or drastically change any Pacific war.  You could even have France, which would probably have moved its capital back to Paris after peace was obtained, allied with the western powers against Japan if it still strikes for SE Asia!

  This presumes of course there isn't later conflict in Europe or the wider world over Nazi Germany and its insane policies and desire for continued military expansion.   Also how complete would have been the Nazi conquest of the SU, both in terms of how far east they reach and how completely they would control the occupied areas against the inevitable [given their occupation policies] mass unrest there?

  You would likely see Algeria maintained much longer, possibly until the present day if the Nazi regime survived and if enough ethnic cleansing was used in the colony.  Possibly also Morocco and Tunisia as they would otherwise be important centres of support for Algerian resistance, presuming Tunisia isn't given to Mussolini for his 'contribution' to the war effort.  Although if non-French were expelled from Algeria their likely to end up in those two states.

  More difficult to see them holding areas further afield, although they would probably be most interested in Senegal and adjacent areas, modern day Mali and Mauritania as those link up with the N African colonies.  However unless you end up with an extreme racist world with massive killing, which might not be impossibly, anything further afield is likely to be too much and even those areas of the Sahel could well be beyond France.

  A lot would depend on what happens in other European colonies.  How long would they resist decolonisation and to what degree?  Its a lot easier to hold a colony if its borders are held by other colonisers who oppose independence movements.  Germany will want to regain some of its 1914 African colonies but probably won't get them all back and are likely to take the Belgium Congo as they desired that in WWI so with ultra racists in control things are going to be bad there and ditto, although possibly not quite as bad in Italian colonies.  Spain and Portugal will have right wing at least semi-fascist regimes and as long as Germany is controlled by extremist and dominate the continent that's unlikely to change although Portugal especially would struggle to maintain its large African colonies and might end up selling some of them to Germany.

  Britain would be the big uncertainty here, depending on the peace terms, what government and democratic processes are in place at the end of 1940 and how the British population responds to the defeat.  [Plus other factors such as how much needs to be spent on home defence and possibly in a near term war against Japan.]  You could see it as the last large democratic state in Europe seeking to liberalise to reduce its own spending and gain support in the former colonies - as none of them are likely to welcome the alternatives, or resentment plus possibly a boost to fascist ideas means there's a determination to maintain the empire, either as a demonstration of continued British power or because its seen as a source of strength.  The latter approach is likely to lead to early and serious problems in India of course which could see a lot of blood split before independence is gained there.  After which does Britain double down on other colonies or do you see a more rational approach with a liberal stance becoming dominant?