Don't get it wrong, your two cents are really appreciated! :)
I've been using Steam for a while, but just for playing; I was totally unaware of the donation feature.
I'm thinking of adding a fourth ending, yes. Another very difficult thing, for me (as for many others I guess), is to decide that a project is finished and nothing else should be added! :D
Nevertheless, the "opponent" can actually be sent to the shadow realm... It's quite a hidden mechanic, probably, but far from impossible to discover. :)