I went through a similar thing 2 yrs. ago. AH went to a tax preparer that his addict friends used. He never asked me to file jointly. Showed me the paperwork and simply not done correctly. "Smart me" haha-told him the changes I thought should be made and that I would file jointly with him to get the extra deduction but would not pay what he owed. "Smart me". Well, he is sent to prison and I receive a letter from the IRS wanting the money he owes. Hmmm. I ignored them. Then a registed letter stating they are taking $100 out of my tiny social security check-THAT HURT. I called them and explained the situation and they were actually nice, had I called they would have done something different but too late now. Both said too bad he was not in federal prison-they would send him a big hello.
I was in banking almost all my life and dealt with the IRS many times for customers. I have found that they are not the devil and will work with you whenver possible. Be certain when talking to them to document the conversation and their names. The IRS should be able to advise you on what steps to take.
Hang in there!!!!!!!!!