Goodness, Nurse was kind enough to link to my log. I'm flattered.
First, you're already lifting some good weights, so congratulations. You're about at my level.
Second, years ago I went through some rehab (or "prehab") exercises under the direction of an ortho specialist. Very similar to mobility and balancing exercises described on T-Nation. They're recommended for all lifters, and I think they would help you a lot. You learn how to control your back and the muscles there, how to stay balanced, keep good posture, etc. Train on how to arch your lower back - it's invaluable for all 3 PL lifts.
Be patient, train your back and get the muscles good and strong. Don't worry about a belt for the moment - make your core strong enough to hold itself. Work sides and abs, get your torso tough.
I wear a heel lift when lifting, it helps tilt my pelvis and somewhat corrects for the scoliosis. You might have to twist the hips a bit during squat or DL to get more balanced.
Also good idea to hang from chinning bar between heavy sets of squat or DL to help decompress spine.