My opinions ... for what they're worth...
I realize the original question was about vests, but aside from the "tactical" issues, a load bearing vest is a horrible idea for anyone with a lower back injury. A chest rig is probably an even worse idea, since they make you more "front heavy."
If you want soft body armor, get just a vest. You'll get some protection, not that much added weight, and it will be distributed front and back.
As others have mentioned, the long Glock mags are not a great idea for reloads. I don't see a problem with having one in the gun on your nightstand, but for reloads they're going to be too slow. Your most likely need for a reload will be to fix a malfunction, not to feed more ammunition, so you need to be able to get your weapon operating ASAP.
If you want something you can don quickly that will carry some gear, get a good duty or military type load bearing belt. The versions with padding are exceptionally nice. Add a couple of mag carriers and a good holster (with the mags and your pistol in them, of course) and you're good to go. You'll be able to get it "on" at least as fast as you could a vest and it will be far kinder to your lower back. You could also add a flashlight and your cell phone to the belt, and you'd be good to go if you have to move from one location to another in your home.
Another thing is that if your back is bad, a shotgun is also not a great idea. If you can tolerate shooting a shotgun for any kind of practice, you're probably not that bad. If you are in a bad way, that kind of stress is not good. The AR (since you have one) is a much better idea, more versatile (for defensive use), etc. You'll probably want to keep a set of electronic hearing protectors with your rifle though. If you have time to get the rifle, you have time to get the earmuffs.