Who should get the house - son or stepmother?
Inheritance of the home depends on who it is left to when the owner dies. If your father in law does not write a will, inheritance of the house will be governed by South Carolina law (called the "Intestate Law."). I do not know the details of that law. Your father in law's wife would inherit at least most of the house, and possibly all of it, depending on what that law provides,
It would be highly unfair if you and your husband received nothing from the house, after the work and money you have given to it, and your father in law. The easiest way to make things right is for your father in law to write a will, leaving you at least some portion of the house.
I cannot tell whether your father in law would want you to receive all the house, or only a portion of it, some percentage of ownership. That is up to your father in law to decide, assuming he's willing to write a will.
It may be difficult for your husband to discuss writing a will with his father, but I suggest your husband make the effort.
You state that you are not in a position to have the house put in your name. So your father in law cannot simply give you the house (assuming he was willing to), whether by quitclaim deed or other deed.
