Hello, I'd like to help you with your question.
It sounds like you have tried everything you can think of to deal with your husband's problem. But no matter what you try, he has to want to accept help and do something himself. It does not sound like he is willing to do that, which leaves you to decide the best way to help yourself and your children.
It is understandable that you feel bad about leaving. But you are right, you have to consider your children and your own needs. If you all are becoming depressed over the situation, then you are being affected to the point that you are having trouble coping. This should, ideally, trigger your husband to get help. But either he is too depressed or too focused on his own needs to do something about the situation. Unfortunately, that means you will have to.
It is ok to leave your husband. You are not leaving after a short time of this behavior but instead you waited 22 years. You have tried everything to change the situation. There is no other solution in order to protect your family. Consider talking to a counselor about your feelings. You have seen a lot of therapists, but just having the support for you and your children can help you cope with the loss of your marriage and the stress
you have gone through being the only partner to work on the issues in your relationship. You may be carrying around more stress than you realize.
Also, consider building your support now. If you have family and friends that are supportive, talk to them about how you feel and let them help you. Spend some time away with your children if possible just talking about what you feel and focusing on your relationships. If you attend church, reach out to the pastor for support. They are usually very good at dealing with marital issues and divorce so they can offer guidance.
It may take a while to work through this but you will. Even if your marriage was not the best, XXXXX XXXXX still a loss to you of hopes and dreams. Give yourself and your kids time to heal.
I hope this has helped you,