Spook, I really do understand why you want to do this - you feel you must give your best effort to something that means the world to you.
I just fear that your dh is not ready to be completely commited to you and is going to hurt you again. If he stayed away for a few weeks it wouldn't diminish your chance of a future together. Tomorrow is another day, and he needs a few tomorrows to gain a bit of maturity.
You are very loving and kind to take the weight off him. But what is he learning from this? I worry that to him it just might seem as if once again he does not have to take any note of your needs, and the damage he has inflicted on you. He ought to be contrite and caring, you should expect it of him, not relieve him of that responsibility. If you don't expect much from him, you won't get much. Please don't let him drain you of all your emotional energy. The world does not revolve around this man, even though you feel it does sometimes. You are equally as important, and your needs are vital.
How are you going to explain to your sons when you are ill from coping with it all, and have nothing left to give them? His coming back and going over and over again is one fresh wound after another, not just for you, but for the children too.
It is not a gift to your family if you wear yourself out caring about others' needs and put your own at the bottom of the list. You will be a more vibrant and attractive woman who commands your husband's respect if you push your needs forward. Ignore them and you will feel like a doormat, and your husband will continue to treat you like one.
Unless he willingly addresses your needs, he is always going to drain you emotionally. Please don't put up with it.
I also note what has been said about taking advice from a solicitor and I strongly urge you to do so. You are in an enormously vulnerable position and you need to take measures to protect yourself. If, later, you find you don't need them, all well and good, and no harm done. However, if you haven't covered your back, and your dh lets you down, it will be hard enough to cope without having to worry about losing your home too.
That is my advice. But I want you to remember that if you do choose to ignore it, you need never fear that I will not be here for you any more. Whatever you decide to do, I am here for you, regardless. Why isn't your dh saying this to you? Demand more.