Should we just stay out of it?

One of my best guy friends is miserable in his relationship, but he doesn't want to end it 'cause he's too nice a guy to hurt a girl like that. They've been going out for about a year and 3 months. A couple weeks into the relationship he tryed to end it with her but after she dropped a few tears he took her back. That has happened a couple times, where he tries to save himself but ends up being sucked in deeper with her thinking he actually loves her.This girls a first cl *****. She's uninteresting, mean spirited and not even good looking (i'm sorry I know thats mean but i'm a little pissed) She bitches and he bows his sweet little head and takes it. She starts petty fights and he sucks up to her so she doesn't do anything stupid to herself. She makes him miserable while she's all chappy-happy. The look on his face when he's with her screams "save me now". All his friends can tell he doesn't wanna be with her but he doesn't have enough to break it off with her. My biggest problem with her sprung from her intense jealousy of his best friend, admittedly said best friend (lets call her Sam) is moviestar gorgeous and could bring out the green eyed monster in anyone but everyone could see that there was nothing between them, they were just best friends who got each other. Even though "Sam" tried her very best to ignore the building tension and even tried to smooth it over the jealousy never subsidded, it just worsened to a point where he was forced to stop talking to "Sam" and I. Ever since this jealousy thing started he hasn't been the same, its been like he's PMSing 24/7. But today they had a fight and she stopped talking to him, for a day we remembered what it was like to have the old him back. We want to keep him like he is but know that once he settles things with her, she's gonna go back to sucking the life out of him. We've been trying to convince him to dump her *** but he just smiles sadly and looks up at Sam and I. I think I understand, he can't break up with her, he knows it will destroy her and he'd rather have it crush him than to do that to someone who used to be his friend (yes, he really IS that nice). Sam and I don't know what to do, we hate to see him do this to himself but we wanna stay out of it as much as we can (which we haven't) "Sam" has nearly given up and i'm contemplating it too. So should we stay out of it and wait for him to grow or should we intervene like the bossy alpha female within us are screaming to do?