Well, you know they say that hindsight is 20/20. So, even though you asked your H to leave, you can do what you can to make yourself become the kind of person he would want to come back to. What can you do to at least open a line of communication between you and your H? He already knows how you feel about everything, so to bring that up each time you do manage to speak to him, is not helping. I am not sure you are really trying. As for holding it against your MIL, if she is ill, that might just be taking up most of her thinking. I mean, a lady who needs round the clock care is hardly going to give her full attention to this.
Re your house, do you need to sell it? Are things okay now, financially? Because you are right, you would probably get nowhere near what your house is worth in this current market. As for you D your H, and him marrying ow, is she or is she not still married to her H? Does she have kids?
And this does not have to be a no win situation. You have to first want to help yourself if your situation is going to change for the better. You really have to want it. And then develop ways to make it happen. It isn't going to just happen. It won't be easy, but if you REALLY want it, you can do it.