You do need a good lawyer.

Will the house belong to you but he pays mortgage? + 4K per month? Depends how much the house worth and how much his business worth, it seems to be not too bad a deal. (You can ask him to put more cash into the house. In case, in the future, he stops the payment. You should also ask for half of the money in the IRA accounts.)

At same time, if he has a business here, it is less likely that he will go back to China. A good lawyer will help you. Sorry that I don't know any.

Good luck!