Thanks so much. Explanations ahoy!
1) Linux version is already there. You have it. It's the .love file inside the .app on this site. You'll need a slightly earlier version of Love2D though, but after that it works perfectly.
2) Steam: As you say, I got greenlit. But then I looked at:
a) How much work would be required to do all I wanted to do to it to make it a suitable Steam release.
b) How little interest this game seemed to generate when I released it for free.
...and suddenly realized it was not really commercially viable. Shooters don't sell. Steam users are super-demanding . I wasn't sure it was worth the extra effort considering the overall lack of enthusiasm I was experiencing.
As a result, I've been working on other stuff instead. I hope that answers some of this?