It is really hard, but your son is of an age when he can chose what he wants to do and if his dad persists then he will lose him for good.
I have had this with my son when he was 13 he stopped wanting to go round when told to, he wanted the choice; his dad was unhappy with this and for a time they stopped seeing each other.
Eventually, his dad agreed that he would be more flexible and understanding, so gradually they got back together. Silly thing in all this, he still goes to his dads every Monday but knows he doesn't have to so it works; he also goes occasionally to watch football with him and they go on cinema dates.
He dad still doesn't like it but knows he has no choice.......... he moans to me but hey at least my son is happy.
Recently they went to California for 2 weeks, they have never spent so much time in each others company; they came back having had a a great holiday and more respect for each other.