This discussion also brings me back to the singer in my ex husbands band. They were signed to a label in LA; the whole bit. I won’t speculate a diagnosis but the singer fell into the master manipulator category as well. It was both fascinating and horrifying to see what he could pull off with industry professionals and the advantage he took with things. 100% self serving and zero empathy for who they trample in the process. He burned many a bridge.
People like this give me huge pause once I recognize the pattern. Hearing your story so far OP, would keep me firmly is the very clear and documented communication of no, and just keep the relationship professional.