I think separation is a good choice.

you can see if you can live well without his care. You might regret latter, you might find this is a good decision. Whatever. The most important thing is that you tried when you want something really badly. You are still young, you have the luxuary to try whatever you want. before 40, no fear, after 40 no regret.

If you feel you owe him because of greencard, you can make up by giving him some money. You can not want everything.