First of all, my sympathies for the broken ankle. I broke my foot 3 months ago and my squat went from 255 to 165. Fucking sucks.
As for your lower back, I get that stiffness very often. I suggest you completely lay off the squats/deadlift for a while and wait till you heal. If your injury is similar to mine, then it's not a big deal, I would think.
Also, make sure you keep your chest UP during squats. Leaning forward kills my lower back.