You are acting in self preservation mode. That isn't uncommon but you really need to work yourself out of that state. Its destructive for him and your own well being.
And it starts with honesty. With him and getting really honest with yourself. Its hard to break down that wall. I know the pain all to well.
You have to ask yourself first, do you want to be in a relationship with him. If the answer is yes, then stop hurting him. You choose only yourself when you take your comfort above all else. And if you want to go about this the healthy way, its going take a lot of uncomfortable feelings on your end. You will have to step out of your comfort zone and do things you've never done before.
You've done significant damage to him far beyond your cheating. I cannot imagine the toll of years and years of gaslighting and mental abuse and how its effected him. Its staggering to contemplate. Its going to take a lot of work from both of you if he's ever going have a chance to recover.
You need IC and I would even suggest it for him. You need a qualified therapist to help you, I believe many of your core issues are in your FOO. You need better help than the what the internet can offer you. Nothing is going to change until you are ready for advice and counseling.
You can go from toxic partner to a safe one. But it has to start now. You have to take steps in that direction. Surviving infidelity is tough. The odds are against you. Thats just a fact for all of us. Maybe you can educate yourself on trauma brain, grief, things he is experiencing. Read in the Healing Library here too, find an article called Joseph's Letter. Prepare for what you are up against. The more you know the better.
You have mentioned all the things you've done wrong. I'm curious what you have done right if you are up for sharing. We can help you add to the positive things.