1) Not too much. Soviets easily could have helped Warsaw in 1944, however I think they really were exhausted and any big scale operation was temporarily out of the question.
2) Reduce, certainly, assuming all Eastern Europe is "finlandized". Humans rights are not broken, free-market economy works OK, nobody murders or imprisons AK soldiers or Free Polish soldiers. Poland enthusiastically works on rebuilding itself from devastation, so is Eastern Europe
3) See point 1. However, assuming it happens as you said, the Soviets are able to crush Japanese army in Manchuria a few months earlier (in spring 1944), occupy whole Korea, Sakhalin and Kuril Islands and start bombing Japan. I'm not sure if they were not ready for a really big sea-landing operation, however with total air superiority they might try invasion on Hokkaido.
And now I can tell you why I think it is hard to imagine. IOTL Poland was supposed to be totally independent, not just finlandized. Stalin promised the Allies that and that he would allow free elections in Poland, but of course he lied. Why should he go for finlandized Poland if he could have communist Poland as an open gate to Europe? Even if you eliminate Stalin I doubt if any of his successors would have accepted that solution and kept power after that. Remember, the communists truely believed they bring joy and happiness to conquered peoples.