Generally Social Security benefits cannot be garnished. However, be sure that you do not co-mingle your benefits with other deposits on that account. If you put your benefits into an account that you put other money into, then that may make the benefits capable of being garnished. The safest thing to do is to have a separate account solely for your SSDI benefits. Good luck!
You are correct. Student loans have several options available when individuals can not afford the payments. There is a deferment for unemployment, forbearance, public service forgiveness and income based payment options. If you visit the Sallie Mae site they have a whole section devoted to the available options.