Well 2) works for me (in Unity), so I can't really help. But for 1, it's because Nautilus, besides from being a file manager, also controls your desktop and will happily take over it when started.
To disable this feature, install the package "gnome-tweak-tool". Type this into the terminal:
(I added the --no-install-recommends flag since apparently it pulls in some unneeded GNOME packages)
sudo apt-get install gnome-tweak-tool --no-install-recommends
Then launch it, go to the "Desktop" section and disable "Have file manager handle the desktop".