I think you're confused. Try not to jump to conclusions about what he means - ask for clarification first.
I read his offer as this:
He will pay the mortgaqe for 4 years. After that, he gives you the equity in the house in exchange for your share of his retirement assets.
In that case, his paying the mortgage for 4 years wouldn't necessarily be part of your alimony. It sounds like it would be on top of your alimony?
Now, this may or may not be a good deal for you. You need to do the math. How much is his retirement account or pension worth? How much is the deferred comp worth (or, if he spent it, how much was it worth?). How much equity is there in the house currently? Depending on these factors, it might be a good deal to keep the house IF YOU CAN AFFORD TO KEEP IT AND NOT END UP IN FORECLOSURE, or it might be a better deal to split the house equity in a few years and split his retirement accounts.
The worst outcome is if you give up your interest in his retirement for the house, then fall into foreclosure because you can't afford the house - then you end up with nothing.
