Sorry, the PE can not use Hulu at this time, and I don't think it will be able to any time in the near future
Yes, epubs/pdf files from gutenberg and manybooks should work just fine!
Calibre should work fine for converting your ebooks, you can see a full list of supported formats here:
link
I'm not sure about the calendar sync, it looks like it is possible from a quick search, though I can't promise anything(you might want to see this:
link
At this time I don't think that the WOSD is caused by the update, but rather wear and tear on the hardware, and I don't know if anyone is still going to accept returns, you would have to read through their policy to see if they would accept devices that have lost support from their company...
I hope this helps, let us know if you have any more questions!