Not sure how to help with this but as a temporary workaround you can append an "&" after the command to make it run even after the terminal is closed. Should look like steam --restart &.
Ah, so apparently it's been removed from the Ubuntu repos. I would try apt-get qtile if you haven't already and if that fails, I just wouldn't try qtile. I'm not sure why they removed it from the repos though.
i3 is configured in it's own configuration language thing which I personally find very easy to use and understand. Fluxbox on the other hand is, I believe, configured through a GUI though I've never used it so don't take my word on that. Btw awesomewm is written in Lua not Python. Didn't realize my mistake until just now.
If you're looking for a floating wm then Fluxbox might be your best bet. Otherwise I'd try i3. It's easy to configure and has a lot of documentation (it also features a floating mode I believe). If you're looking for something in python then I would recommend either awesomewm or Qtile (my fav). Qtile is a bit more difficult than awesome to configure though, but it has a better status bar.
Not sure how to help with this but as a temporary workaround you can append an "&" after the command to make it run even after the terminal is closed. Should look like
steam --restart &
.