Reading all those posts and while the decision itself is easy, even though the actions definitely aren't.
However, I would agree with everything everyone else has said here. Whether he's cheating or not doesn't matter if he's treating you like this. I think that any man who tells his partner that they're worthless clearly has some issues! I know looks shouldn't count here but I can't imagine you would be short of attention.
I can only imagine that he either has his own esteem issues and needs to make you feel weak and unattractive, so that you don't feel that you can get better than him, or he gets off on this level of control knowing how you feel about him - that's bordering on sociopathic. If he's addicted to porn then that's his problem and I'm not sure that even if you helped him with it woud change your relationship.