I think OP you are in big denial here. I have been in your shoes and my marriage has survived so you can get through this. Both DH and I had counselling - me primarily to deal with codependency and building my self esteem so that I would not tolerate any of these behaviours from my DH, putting appropriate boundaries in etc.
You really cannot comprehend how bad his gambling can possibly be. My DH put over £25,000 over the counter at the local bookies alone. He bet online, he did spread betting, he bet on anything, football, golf, tennis, the horses, literally anything. When he should have been working, he was studying form - you can imagine the dire straits the business was in. I had 4 young DCs, 2 with special needs, at home. The final straw was that he had an affair with a woman who worked at the local bookies (you couldn't make it up
). As much as I hate to say it, his affair was the thing that saved him and our marriage, as far as he was concerned that was his rock bottom due to the type of woman she was.
He has had many months of counselling to understand his need to test himself and self destruct. He had a need to put himself in perilous positions to see if he could extract himself from them. It wasn't gambling as such that he needed to reach a high but the adrealine of getting into a tight spot, trying to find the money to gamble, so many different facets to the whole thing. He has really struggled with himself during recovery, episodes of depression etc. It has been far from easy.
He has found better ways of dealing with stress now, getting "highs" from other areas eg running, tennis etc. Giving himself targets in that way.
You really need to step right back now, protect yourself financially, maybe get some counselling yourself to understand codependency etc.
Only your DH can cure this and control this, not you.