I think the chances of keeping the house depends on how amenable your soon to be ex is to getting the portion of the equity. Do you even have the money outside the retirement account to do this? Wouldn't that money be considered marital property also?

Kind of sucks to be in this situation to be honest. You need to discuss with an attorney as to what is the best possible way to do this and maybe persuade her to take some kind of note on the equity.
It would help if you can more easily afford the payments, but at the end She would need to play ball. You don't want to get into a situation where you end up paying thousands in legal fees on top of half your assets.