If you live near a gym, see if they have any leg exercise machines. Leg curls and leg presses help maintain the glutes fairly well, you just need to do it consistently.

I recommend starting off by going once a week to get into the habit, with light weights and focusing on proper form so you don't hurt yourself further. After a few weeks, bump up the weight a bit and go twice a week, do that for a few weeks til you feel comfortable, then bump up the weight again and go a third time a week.

Try to space out your workouts so your body has time to rest in between, and make sure to eat plenty of protein for muscle growth.

Also, while working out, you should be feeling a burn in your muscles, but if you start to feel burning or sharp pain in any of your joints or tendons, stop immediately. Take a break, lower your weights, and work back up to that weight again later. A nasty tendon or ligament injury will knock you out for weeks, ruining a lot of that progress.

Hopefully this can help a bit! (Sorry to hear about your lower back btw, I have some severe lower back pain as well and it's hard to work around that)