It's really hard to quantify improvement with exercises like that. For me, it's enough knowing that my form is improving, and I can do more reps, and I can do harder variations... but tracking that is a whole other thing.

On the back pain front, my chiropractor talked me into giving yoga a try, and it's great. I've hardly had any pain at all in the two months since I started. And for me, knowing that my form is improving is enough to keep me coming to the classes, but YMMV.