Your H is a runner. It keeps him from having to face himself. My H is too, but his choice of running is work.
I agree with Bond that it is a set of choices, but I believe MLC is a form of mental disease. Not an excuse, but an explanation. The fog they're in allows them to justify the choices they make.
For a MLCer to make it to the other side it takes deep introspection. The facing and making connections to wounds that happened long before you met them. In many cases IC to help them understand and settle those internal issues.
It has been my observation that MLCer's try multiple methods to try and outrun their pain. Reality eventually smacks most of them right in the face and they eventually realize that the grass really wasn't greener and they are no happier and in many cases a lot less happy than they were before they left. Only now they have to face the destruction they caused.
As a mom, the hardest thing for me to deal with was the hurt to our children. When I accepted that I could do nothing about forcing H to be a good parent, I have let it go and stepped up for my kids.
What your H is doing is typical. You have no control over this. You only control yourself. Regardless of what he does, your boys know you're the one that is there for them. Unfair that it is you have to fill in, to the best of your ability, the gaps that your H has created.
You're doing well GM. It takes time to navigate your way through the chaos.