OP, it's so sad to read all of this.
You obviously know there's a lot more going on even than your OP suggests.
Nobody on here can sort that out for you - but I will just add to those who say that you are doing an enormous amount with your teenagers, just by being there. I know it doesn't feel as if you're doing anything at all, but you really are. You are the solidity that enables them to go off and do their hobby with your DH, means they will no doubt go on and have great adult lives, etc, etc.
FWIW, my experience of teenagers is that there is no 'one size fits all'. I have loads in common with my 17 yr old (son), but the only thing I have in common with my 15 yr old daughter is that we are both female.
My 17 yo does some stuff with me, and lots of stuff with his friends. My 15 yo sulks in her room and appears when she needs food or money. She spends all her free time with her friends. That said, she does talk to me - though only ever when I'm dead tired and about to go to sleep.
I don't have a TV either, and never have had. However, I've bought a TV licence so DD can watch TV, and I have sat and watched things with her on her laptop. Some of them aren't my cup of tea, but it is good to see what she's watching. She's always quite friendly when we do that.
I know that your problem is very different - but I suppose I'm trying to say that there's no guarantee that you would see your DC even if they spent less time doing their and DH's hobby.
(This, obviously, doesn't solve the DH problem).
I was on the other side of this, too, in that XH did absolutely nothing with our DC, other than abuse them. I can also tell you that EOW doesn't work with older teenagers; they come and go as they please. Yours might be a case for mentally detaching yourself from your marriage, whilst staying physically present. I suspect your DC haven't got a clue that anything is wrong, and divorce is a very long and hard road, with no guarantees at the end of it.