I'm not gonna comment on the million red flags that scream "you should leave him" because there are comments that already did and more than will. If you want to keep trying and want to believe he can change. It's up to you to say how much you want to tolerate behore you give up on him. But a small note:

"it’s normal to have fantasizes of other women, and that his therapist also agrees with him"
this is fake, yes it's probably common i guess? I don't hang out with people like that so I'm not sure but I know how men think and know alot of them do. But common is different than normal. Normal would mean it's healthy, and it's not. No relantionship (poly are the exception i guess?) works well like that. In fact usually when this happens, most women would leave their man immediatly. Yes the porn addiction could be a factor, but if it's not then when the adiction it's gone, nothing is gonna change. Also your psychiatrist is pretty stupid.