if he were to live a bit longer, though, with hence a politicla stalemate of sorts remaining between him and the government, could Romania theoretcially join the CP late in the war if it looks like the CP for some other reason are winning? I dont really think pure co-belligerent status as you suggest is feasible, I rather think that any Romanian declaration of war against Russia will have France and the UK declare on Romania, and the Romanian politicans will know that, too...
Sure - if you look at the World Wars all sorts of nations jump in and declare war once they feel sure that they know which side is about to win. Turkey even declared war on the Nazis in the last months of WW2
Best Regards
Grey Wolf