Where to start.
I guess ill just work in the order they were posted.
With switches I have seen, the switch itself is held in place behind the plate by two friction-fit mounts on each side of the switch hole - push the switch back to remove, push forward (until it clicks) to install to the plate. From the picture it looks like one side has been pushed back. If the mount on that side is broken then the plate (but not the switch) will need to be replaced. If the mount is intact, just push the switch forward to correctly re-install.
Make sure you have isolated the switch first before attempting anything.
Not in this case, as pointed out above it is the actual rocker of the switch mech. If you keep using it like this eventually the white plastic rocker pops out and a couple of bits of copper follow leaving a nice hole into some live bits of copper.