Alright, this is a subject I know too much about. I ruptured my L5 when I was 22.
First off your back; this is the most important. nothing else works when your back is out. DO YOUR STRETCHES. I know your Neurosurgeon doc has given you some stretches, make sure you do them. The most important part for you now is to build your stomach and lower back muscles so you can get a tightness around the spine you do not have now. Light crunches and laying flat on the stomach and pushing up your torso while heeping the hips and legs flat to the ground. Hold the position for 1 minute and release. These help with the tightening.
Training with bad back: SLOWLY work into it. Avoid sitting presses and any sitting that puts weight on your lower back. Do military presses standing up. Light squats for the legs for now. Hang from a pullup bar and raise the legs up for some additional stomach work.
I have permanent numbness down my left leg and bottom of the foot into the toes from my injury. If I feel the numb area tingle, then I know I need to back off.
GOOD luck my lumbarless friend.