Coming from someone who tore his L4 and L5 the best thing I can recommend for your squat stuff is high box squats (15").
Having the box to pause on take the additional strain off your lower back and will allow you to keep more upright (or at least focus on it if you have bad form). Something to try if you really want to get your squats in rather than leg press.
Class I Total @ 198: 525/335/600 (1460)
"No citizen has the right to be an amateur in the matter of physical training.... What a disgrace it is for a man to grow old without ever seeing the beauty and strength of which his body is capable."