Sure appears to be a real problem. It appears that not only are you jointly liable for his obligations, you promised to ensure his income would remain at or above 125% of the federally determined level of poverty. That means you can actually be required to pay him support if he does not otherwise have an income of at least that amount.
http://www.floridabar.org/divcom/jn/...&Highlight=0,*
http://www.uscis.gov/files/article/AffSuppAFM062706.pdf
as stated in the first link, the only way for your obligation to end is:
the fact you signed this contract with the federal government, I do not believe running away is going to solve your problems.• He becomes naturalized;
• Is credited with at least 40 quarters of employment in the Social Security system;
• Loses or abandons his or her lawful permanent resident status; or
• Dies

