2. Have a look at the output of
You should be able to fix the problem with
ln -s /usr/share/firefox/firefox /usr/bin/firefox
3. I have the same thing with nautilus. There is probably some switch you can open nautilus with to disable the window manager it comes with ( man nautilus ). You should have a look tho in the firefox settings and have it open a better file manager like rox for example.
Hopefully this helps some with your problems.