Well, I do not know anything about NG tubes, or the "criteria" one must fit in order to have them. However I would just talk to your doctor about your main concerns that you fear about dying and the habits you have gone through in the past...and that you need this support, if they cannot take you seriously then I would suggest another doctor, or go somewhere, even if it is expensive...because you are worth it. go somewhere that has a proper ED specialist... ED specialists will always take you seriously, as doctors arent trained in this area, most I don't think understand just what an ED entails.
Just remember that everyone has relapses, and its okay to relapse, as long as you get your feet back on the ground and stay strong after that. 30 pounds is a lot lose but its never too late to start again... i hope the best for you. be healthy! eat! and live!
good luck and stay stong!!