I don't know the answer but I searched the web which turned up this guide. It appears that the game uses lua, models can be created in blender, and it uses the unreal engine. So yes, that should all be possible on linux.

Yes, you mod it the same way you do on windows, but the game is saved in a different location.

I did a full playthrough with the wands are guns mod on linux just fine

I'd be interested in this, too. Tried getting the mod merger to work but couldn't really do it. Then I gave up.