I'd probably try counselling for your son, and family counselling for you all as a unit, first. See if you can make any progress and if a few compromises from both sides can work. If not then I'd say leaving DH would be your only option, although honestly, if your son is in his mid to late teens, it's probably a bit late for all that now. He can move out in two years and by then, if things keep going as they are, they'll be damaged beyond repair. I'm also not sure if things with your son could even be fixed before he turns 18. Two years isn't a very long time to un-do years of drama.
Regardless of whether you leave DH or not, you definitely do need to try counselling and stick at it for a long time. It will give all of you ways to communicate and at least then, even if the family does break up, you have a hope at being able to remain civil, co-parent effectively and not lose your son.
It's very difficult to truly understand the extent of this situation, though. Your husband could be parenting normally with you being a walk over. Similarly, your husband could be coming down far too harshly on your son and it verging into abusive territory. Or, your son could have a lot of unresolved issues due to past experiences in his life and needed help for that a lot sooner than now, which is why things have blown up in the way that they have.
Either way, seek out counselling and see what they have to say. They'll know much more than any of us here when they hear things from all sides.