I have never noticed (1), it seems, i don't use back so often as you people seem to do (is this maybe a hidden usability issue in some application?).
(1) and (2) work fine AFICT, but you should check yourself (update from cvs head).
The problems, i reported earlier with new xinha versions are gone as well. It looks like they were fixed without altering xinha: most likely, there were a few bugs in early ff 2.0 versions for mac os x.