The most interesting thing is that Dan only really liked JK bc he was the one to help him the most. He picked Dan up, let him stay at his home, allowed him to save his grandmother's things, gave him a job at the gym, etc. Like Dan is right, he has been so alone and helpless for so long that any sign of possible kindness was all he needed to develop kind feelings, and with his history of being assaulted and beaten he most likely didn't even consider all his abuse by JK as all that bad. Incredibly fucked up but Dan needed to realize that he built a fake persona around JK who is a terrible terrible person.
Ultimately, I hope he is either contacted for info or to work as a spy because he may be freed from JK and gain some agency by making the choice. It would also be funny as hell to see JK be out-bid for the loyalty and assistance of Dan, but that's just me.