Thank you for the additional information.
Unfortunately, there is no "common-law marriage" in the state of Virginia. If there were, your step-father and your mother would be considered legally married by now, and to get her out of the house, he would have to divorce her or annul the marriage.
In any event, it appears to me that unfortunately, your mother will nto be able to get her money returned. To begin with, if she simply "gave" the money to your step-father, it would legally be considered a gift.
If she had given the money with some conditions attached and can claim it was a contract, even so, the statute of limitation on a contract claim is 5 years. So the time to file a claim for a return of the money pursuant to breach of contract would have been about 2-3 years ago.
Nevertheless, your step-father cannot simply kick you out of the house. He would have to evict you as you have at the very least, tenants' rights. However, if neither you or your mother are named on the mortgage or deed to the house, then he can initiate eviction proceedings to get you out of the house.