Is he entitled to my tax refund?

So I am in the process of a somewhat bad divorce. I am a veteran who owned my home before I married this man and I have a 9 year old daughter from a previous relationship. We have been arguing for months and he has been extremely violent on 2 different occasions. Once last April he caused some serious damage to my house. After weeks apart and therapy we reconciled. And now the 17th of December he did it again. We separated that day. I have taken pictures of all of the damage. And since then things have been very bad. I owned a 2006 Civic (I now owe $8400 on it) when we got together and he had a 2006 Fusion. He traded in the Fusion last March for a 2006 Silverado that is in both of our names that he is keeping. The dealer tacked on $2000 to the loan on the Silverado because the Fusion wasn't worth what he owed on it when we traded it in. We now owe $14000 on it. The day of the separation he was driving my Civic. He wanted the Civic in the divorce and I told him no because it was mine prior to the marriage. Because he was driving it, and I was at work, I was afraid of what he would do. The entire conversation was over the phone. He told me that he was keeping my car and when I told him he couldn't he told me that he was going to "total the car then". (By the way I have text messages confirming his threats locked into my phone) Knowing his destructive behavior as well as I do I asked him what he wanted for the car. He told me that he wanted me to sign a written contract stating that I would keep the car and he would keep the truck but I had to give him our entire tax refund. I understand that it was quite stupid of me to agree, but I was panicked. And mind you still in the process of cleaning up my house from his damage. I am in much clearer mind now than I was at the moment. I left work immediately and we went to the closest bank we could find because he wanted the contract notarized. I signed it and he gave me the keys to my Civic. I left my i.d. on the counter at the bank, on accident, and was shaking uncontrollably. He then threw my i.d on the floor in front of all of the tellers. I filed for divorce already. I signed all of my copies already and gave them to him. I am just waiting on his signature to request a court date. Nowhere in the divorcee decree does it state that I am required to give him the tax refund, it is only on that paper I signed in the bank. I am going to try to speed up the divorce process so that it is impossible for us to file as married. But if we are still married I am going to file married but separate. I live in Arkansas. And I believe that because I signed that paper under duress while he was threatening to "total" my car, that I may be able to claim that piece of paper invalid. I understand that the truck is in both of our names and regardless of the damages I am not a hateful or irrational person. I do believe that he should not walk away from this marriage with anymore debt than myself. I would be happy to give him $3800 which is the difference from the amount owed on the Civic compared to the amount owed on the Silverado, minus the $2000 that was tacked onto the loan from his Fusion. But that is all that I am willing to give. Am I being fair and what can I expect as far as consequences if I do not abide by that letter that I signed? I made over $10000 more than he did last year plus I own my home and have a dependant. My return will be much higher than his and I don't believe he is entitled to it. I know this is a lot. I appreciate any advice I can get. Thank you.