is there no other way we can take this off his hands and develop it and continue it ourselves without the source code? or are we at his mercy?
You can access all of the source code and extract all of the assets. Having him give everything away would save time, but anyone can look at what he did and rebuild it if they want.
The reality is that this game must be done as a passion project. 1k a month isn't enough to pay for proper 2d/3d artists for environments, clothing, animations, etc. Anyone with that kind of talent can earn a lot more money doing a 9-5 boring job, and skip the patreon stress.
I haven't chatted with the developer for a long while now, so I have no insight into what he is doing. I still find the lack of communication unnacceptable, regardless of what is going on.
As for Monkey, continued support will depend on how much effort is required, how many things he broke and where the game is headed.
-T-