When things like this ( the masturbation in the bathroom) take place in your relationship, you must speak up about how it makes you feel right away. If you say nothing at the time of the incident, it will fester and make you resentful, and eventually it will lead to a strain in your relationship that you are feeling right now. Honestly I don't see a problem with his masturbating to porn in the bathroom, but I do see a communication problem between the two of you. Both of you need to talk openly about your sexual needs being met ( or lack thereof). If you can't reach an agreement on that, or if you don't see a positive change in your relationship in the near future, then maybe it's possible that you two aren't compatible.
This involves many things of life like environment, relationship, commitment and tolerance level. Sex is affected by any disturbance in harmony.Talk frankly come to some plan of revival of relationship.
Him not satisfying you, but it is not disrespectful for him to satisfy himself if you did not. Yeah you should be enough but guess what that night you were not so he took care of himself and I am sure he would not mind if you took care of yourself.
Yes, immature is the right adjective to describe him. In fact he does not know that if he satisfy you, he could get more satisfaction from you and he would not need porno to satisfy himself. In fact sex is ideal if both are satisfied at the same time. If both orgasm to gather,it would be full body orgasm.I think you should have a frank talks with him and formulate norms . If he agrees, continue the relationship, otherwise say good bye.