if the IRS is right and it's not asking for an amended return, you don't need to file.
it would also be impossible to file an amended return without his consent.
the $7,000+ will include late payment penalties and interest which alone can be more than $2,000 of the bill (you should see this on the notice)
you mighty want to consider engaging the services of a pro to see if they can get some of the penalties abated. you might even qualify for equitable relief. since it seems your saying that part of the understatement was due to a W-2 for you not being reported and part due to a W-2 for him not being reported, you won't qualify for innocent spouse relief since some of the balance is due to your income not being reported . there may be other avenues open that a pro can discuss with you,
note that your ex may have gotten the same bill and if part of this tax bill is due to his unreported W-2, why should you pay it all
