Solost: I have read this thread all the way through, dipping in and out of it over the last few days. I hope you are ok, and of course your dc are paramount.
However, I do think that you would have H back if he was to ask you to.
That is none of my, or anybody elses business, only you can decide this. But your posts do show that are finding it hard to detach. Personally, I can't understand this, but we are all different.
You really do need to do as advised, and stop blaming OW, and blame him. Remember, she owed/owes you nothing, he owed you everything. He, and only he, is at fault here.
Regarding the finances, I totally understand that he should be supporting you and kids. He is doing this, more than the amount he needs to be, from what you say. But please weigh up carefully the price of your freedom and moving on. If you proceed with a divorce, which covers your outgoings, and leaves the kids adequately provided for, then you will be able to move on. You will force him to accept that it is over. This will I think, give you pride and independence, and will allow you to detach fully, lick your wounds and move on. A few extra quid a month is great - but right now it's keeping you in a cycle which you seem unable (or unwilling)to break. Or, of course, you want him back - which is fine, if you want that. Personally, I couldn't or wouldn't have him back, but its between you two.
Perhaps if you dig deep and ask yourself why having him pay more than he should (and of course he pay what is due - his behaviour has been/is pathetic), is better than being okay financially and free to move on, to get things behind you, instead of being constantly in the same situation you are in, for another few months/years, then may be you be able to be honest with yourself.
I'm not judging you, and I'm sorry if I sound harsh, but it really isn't healthy for you to be in the situation you are in. Your kids need you well and healthy - they need to see a mum who has enough self respect to sort this out - force the issue if need be, and move on. For all your sakes.
Good luck.