Jess...hats off in front of you ,girl ...your words, actions and general way of thinking show a lot of maturity. Life pops all kind of challanges in front of us and on the long run , it's not about the nature of those problems, but about the way in which we overcome them.
Family members are the most important, reliable and sincere persons you have in this world....friends ? they come, they go ...few remain or are worth keeping around
I'm 100% on your side about him having to just keep his mouth shut and have confidence in you about going to the movies (which one btw ? ) with the other boy, a boy that so far, has shown a lot of respect towards you, your decisions, and even towards your boyfriend and the status he has in your eyes ...after all and when all is said an done , your BF was the one that nearly blown the relationship sky-high, not you, so i'll strongly advise him (man to man) to watch and think carefully his future actions and words...you gave him NO REASONS to doubt you so far, so don't let yourself be dragged down in this "toss the trust" uneven game.
My best wishes , Mike ;)