Jujitsu may be a candidate... less kicking than the other arts. Less strain on the spine.
Just make sure your Sensei knows clearly the nature of your injuries.
If it is as severe as it sounds... the Martial Arts you need can be found at either Thunder Ranch or Gunsite...
I would favor a solid "Punch Draw" technique. To keep the bad guy off you and punch a few holes in him quick.
Kenetic Defense Institute