I say screw SSI unless you really, really, can't do anything else. Unless you want to be very poor the rest of your life or trying to hide your other income.

You'd be better off moving to a cannabis friendly state where you can get and use your meds in relative freedom.

And stop thinking of yourself as a liability, man. You're a Marine and you put in your dues; you don't deserve to be kicked around because cannabis helps you to deal with your issues- Marine or not. It should be the right of any human being.