If your husband gets sued, he can ask for this info as part of discovery.
I suspect that the creditor, whether Sallie Mae or a collection agency that bought or has the loan on assignment, really has no legal obligation to give these docs to your husband until it does sue. Frankly, hubby should have requested and kept copies of the documents in question at the time that he cosigned this loan.
Now, for the really bad news. Student loans, like all other loans, accrue interest even when no payments are made. The interest rate probably was set when the loan was made, but some student loans do have variable interest rates. Therefore, even if you had the docs, you still might have difficulty figuring out what hubby owes.
If the creditor does sue your husband, it will be entitled to add attorney fees and court costs to the outstanding loan balance in most jurisdictions.
Moreover, a private student loan has the same protection against routine discharge in bankruptcy as a Federally insured one.
As for what you have read about loan consolidation as a way of getting hubby's name off the loan, I doubt that Sallie Mae has to agree to it in this particular case. Moreover, SM is unlikely to do so with a defaulted student loan with a cosigner who may, in fact, have the ability to pay. The lender is not going to be "that stupid".