Is it ADHD, or something else??

My husband has been diagnosed with ADHD since he was a child. We have been married for 8 years and have two young children. He has tried medication and counseling, but never stuck with anything. Except going out to smoke pot 4 nights a week, because it "helps him".

I have tolerated a lot over the years. Lying, excessive spending, he never takes responsibility and if I try to discuss any issues we have, I am a bully or making a big deal out of nothing.

I thought I was at the end of my rope any times, but now I may really have to leave.

Today while on our way to get a Christmas tree with the kids he randomly tells me he is trading in his car for a truck. When I mention that we can't afford that and we''re supposed to be saving to buy a house, he just lost it. He said I forced him to buy the car he has and it's my fault, he never gets to buy anything, on and on. This is his 4th car in about 6 years! And I had nothing to do with him buying it, other than the fact that I am a complete enabler.

In turn I said we should go home and buy the tree another day because I am not taking the kids to do what should have been a fun family activity while he is yelling and furious. The kids started crying when I suggested waiting on getting the tree. He told them this is all your mother's fault, she ruins everything. Then he got angrier and angrier even though I wasn't saying anything (I know better than to talk once he's in this state). Then he just starts screaming at the top of his lungs for me to pull over and let him out. Finally I did. He said "F**k you!", slammed the car door and left. Two minutes later I got a text he is moving out. 

The kids were hysterically crying asking why did daddy do that, why did he leave, why is he so angry. And I didn't even know. Why? Over what?

A couple hours later he was groveling begging us all for forgiveness.

But I honestly don't know that I can or should stay after this happening in front of our children. They are getting older and more aware and I am scared his behaviors, pot smoking, lack of involvement in their school, etc is going to be more damaging than not having him around.

Is this type of outburst ADHD, or is he just a jerk having a temper tantrum?