I truly feel for you so much as you face the challenges that have come your way.
It sounds like you have made an incredible breakthrough - identifying your marriage as that which keeps you down or brings you down. No one really discusses how we're supposed to face the breakthroughs in the way of ongoing positive action or higher consciousness. Without direction, we can be left feeling our way blindly through such breakthroughs, unable to see any significant light.
Sounds like your focus is very much on your kids. Being Mum to a 14yo boy and 17yo girl, I know how truly amazing kids can be. Took me many years (better late than never) to realise how much my kids have been raising me, in so many ways, over the years. We have a mutual appreciation society happening between the 3 of us. Not only have they helped raise me out of depression either directly or indirectly, they continue to raise me and help me raise myself well above and beyond my depression.
I believe it's easy to see who we are, through our children. When we raise them to a smile, we are someone who instills joy and happiness. When we raise them to excitement, we are an exciting person (someone who excites). When we raise them to a sense of self love, we are someone who gifts them the ability to see their true value. There are times when they will also give to us, in their efforts to raise us to joy, excitement and a sense of self love. Needless to say, our kids certainly raise us to many great challenges which can just about lead us to tear our hair out. In this case, the challenge is to open our mind, experience understanding and work on a way forward together (raise each other).
Is it possible to focus on a number of ways you and the kids could raise each other? Could you become a walking team (getting 'outside the house' time)? A benefit to this may be found in taking the time to recognise a lot of the finer details on your walk, even stopping to smell the flowers (metaphorically and literally). This sensory exercise can also be a welcomed distraction from that self defeating voice in our head. Do your kids have certain gifts which can help you open/change your mind? One might be a bit of an artist, another might be a passionate gardener (who's been hassling for a vegie garden). Perhaps there is an eager young chef.
If you can see this time as your kids helping you to further break through a mindset that tortures you, you may come to gradually feel forever indebted to them.