Re the movies: looks like you are really doing lots. Here are a couple more to add to your list. http://www.frederikseiffert.de/filetype/ is the handiest free file type changer I've used; vlc at http://www.videolan.org/ is pretty raw, but will often play movies when no others can--you can at least see if the movie is playable for free. Julie Z recommends Rosetta http://www.thothsw.com/rosetta/index.html for fixing some movies, and the posters in the iMovie forum rave about Cleaner 6 http://www.discreet.com/products/cleaner.
Cheers--I'm just waiting for the next versions of Limewire and Java to see if I can start sharing again: the workarounds you've mentioned have been discussed before, but a new posting can't hurt in case something new comes up.