First let me address the physical abuse. It must not continue, someone is going to get hurt. Either tell him the next time that he gets physical, you will file charges on him. Do not let him continue to hit your husband or yourself . As much as I'm sure you love your son, his hitting is a wrong way to go. What if he hits a girlfriend, or a teacher then he will go to jail and have no choice.
Not going to school is also a bad sign, if he can't focus, take him to a doctor for tests, something could be wrong. I have dealt with young people that can play games but still either out of boredom, or is ADD or ADHD, and still can't focus on their studies.
Sometimes we have to play tough love with our kids. I believe you might be best to take him to a counselor and see what they say, playing around with drugs, isn't his solution, and its going to probably get much worse.
It would be my suggestion to go down and file unruly charges on him. It is against the law for him not to go to school, and if they would decide you are responsible they could file against you.
You could also check into a drug facility that takes kids his age if you think the problem is really bad.
If he is this bad now, another year down the road is going to bring a lot more trouble and misery for you, unless you do something now, after he is 18 someone is going to pay for it.