I have hit a point there is so much damage I question if I could handle another ride nor do I think she could possibly do the work she needs to do
Just one additional piece to put in your pipe: My ex had an affair when my kids were preteens/early teens. he never left the house, the affair was short-lived, and I DB'd the heck out of my marriage. We had a good reconciliation that lasted several years until he hit 50 and had another MLC. Some of the best years of our marriage actually.
So - I was very surprised to learn, after we split, that the kids were walking on eggshells that whole time after our reconciliation, waiting for the other shoe to drop. I would have said that things were great and the kids were secure - but they weren't. Maybe they knew something I didn't?
Anyway, my point is - if you're thinking of reconciling for your son's sake, it might not work out the way you think. It might actually even make him nervous, make him feel like he has to wait for the next disaster.
If you are considering it, I'd say at least a year of good behavior on her part, working on herself, learning to be alone, then MAYBE. But I also think you don't have to feel obligated. I know how seriously Catholics take their vows (I did) but I also think at a certain point, when you've been thoroughly fired from the job, and you did everything you could to prevent this - you're released from your obligation.
