So you currently have no dev team to work on the unfinished product you have been left with. It needs tons of work to be even remotely profitable.
So I suggest this: Start Rune Remastered on Steam Early Access. I would buy that, hell there are still thousands playing Rune Classic. You then already have the basic idea of what to do and assemble a small-ish dev team to work on that. Let Rune 2 sell what it can, bring out a few token patches to fix major bugs and basically leave it. Don’t fall into the trap of sunk cost fallacy.
This ship has sunk, but you don’t have to sink with it.