"...Do you really not get what it would do to me to just stand by and listen to descriptions of you dying, not for the first time apparently, while not even trying to help? I'd never be able to look at MK in the eye, or myself in the mirror again."

He focuses on Max. Considering what this guy might want. The request for a kiss from a stranger was one clue, and a discussion about his role in the world is another.

"Being in a position like yours seems like it would be lonely. What if instead of sending me back, you keep me around? I'll make myself useful as a companion in whatever ways you like, with the caveat that nothing you get me to do has any direct or indirect negative effects on Cole or anyone important to him" -- so, no putting him as the first peg in a Rube-Goldberg Machine that ends in sadness -- "and if a situation arises where he can't get out of a jam, we make a new deal?"

Sure, it's somewhat open ended. But if something happens where it's an emergency, Max will have Macaque over a barrel and he'll probably give almost anything to be able to get in there and help. By the look on Macaque's face, he knows it. That's the deal.