Why does iTunes Match hang on Step 3 on files it has already processed?
Have you tried deleting the iTunes preferences files? You can find them on ~/Library/Preferences/com.apple.iTunes.plist and com.apple.iTunes.plist.lockfile
Erasing them will force iTunes to "start fresh" and hopefully fix the problems you have. It won't delete your data (songs, playlists, etc), so it's quite safe to try it.