Separated, husband selling house

We have been separated for 8 months and my husband is selling the house to a family member. He owned the house before we got married and my name isn’t on the deed. Assuming a 50/50 ED my “share” of the mortgage paydown is about $5,300. His family member has emailed me to persuade me to sign whatever is necessary to let the sale go through, but I need to make sure my rights are protected.

We do not have a separation agreement or a free trader agreement. Without getting into the larger issues, my husband is guilty of all of the financial/economic forms of marital misconduct and is now unemployed (but with $17,000 in his checking account) and I am certain he will try to weasel out of giving me anything (“Bad Faith” is his middle name). He has wasted the equity in the house and not kept it up to the point that the sales price would only cover the mortgages. What can I do? Thank you.