Your question is a legal one, I am a long time Realtor and not a lawyer. If the facts you offer are substantiated by a court, your efforts to regain the home may have some standing. If in fact your stepdad only scratched his name on a quit claim deed, probably your lawyer will be able to show fraud and theft of a home that was (I assume) destined to go to you on your Mother's passing. It would need to have been witnessed and probably filed with the county, in many states a filing fee would have needed to be paid (or a transfer tax) which would show that the effort was done with your mothers approval--her free act and deed--so to speak.
On the other hand, if the quit claim deed was delivered to the Probate Attorney by your step dad, and it is not properly executed or seems fishy, then you need to protect your ownership--legally. If nothing can be settled, or if the lawyers are too costly, maybe you can take the high road and offer your step father a "life estate" in the property so long as he does not contest this offer and he pays all the expenses, taxes and upkeep on the home--full ownership of which will revert to you on his death.
Families often fall apart over money and assets--maybe this will help.