Aight, so the film makes some delusions blatant but I think that it leaves some under the surface. I don't think that he or his standup clips appeared on the TV show, it was just a natural place for him to rely on for his issues given how he had turned Murray into a father figure. His delusions are largely driven by stressful or traumatic events, so he could have legitimately met Thomas Wayne and had a series of delusional events that lead to the climax of the film. I think that he had a narcissistic interpretation of a protest that didn't involve him and killed Bruce Wayne's parents. Also his psychiatrist at the end was the same one as before which could suggest that he's been in Arkam all along, but I don't think that's the case since she said that the earlier psychiatrist office that he saw her at was closing down. She could've just gotten a new job. Idk if I read it on here, but I read somewhere that this joker was the person who inspired the joker in the Dark Knight because the Heath Ledger joker talked so much about his father and I think that's a pretty strong case.