No, you don't have to be responsible for his back debt. If you file a joint return, you can simply file an injured spouse Form 8379.
Here are the steps in the program:
- Sign in to your account, select Pick up where you left off
- At the right upper corner, in the search box, type in "injured spouse" and Enter
- Select Jump to injured spouse
- Follow prompts
- Make sure to skip the screens related to the innocent spouse.
