Can I Get an FHA Loan With a Credit Score of 600?
Yes you can a mortgage with a credit score as low as 580

Does my husband need my signature to refinance?
Since you were on the loan and title, you would have had to sign paperwork and if he did this without you, that was illegal and yes he could get into trouble. I would definately look into getting a good real estate lawyer so you know what your legal rights are