First off I'd try using this link: http://www.pspmod.com/forums/search.php
The answers to about 99% of your questions can be found there.
If that doesn't work, though I don't see why it wouldn't yield any results, this thread was started a day or two ago...it might be useful:
http://www.pspmod.com/forums/showthread.php?t=14638 (Hiya, forum peoples.)
For that last part, if you drain your battery down to 25%, then plug it in, the PSP still registers the battery at 25% so no, it would be reading 100% all the time.