Tweaked lower back during warm-up squat

I'm a 40-year old male, 200 lbs, in great health, with no history of lower back injuries other than a minor tweak when I was 14 that had me in pain for a couple of days. I started barbell strength training for the first time about two months ago. I started with just the bar on squat to focus on form, so after about six weeks I was up to 125 lbs.

The day after Thanksgiving, I was at the gym doing warm-up squats. I did a set of 5 with just the bar, another set of 5 with 65 lbs, a set of 3 with 95 lbs, then started on a set of 2 with 115 lbs. What I seem to remember is that near the bottom of one of those 115-lb warm-up squats (it may have been just before or just after I started to come back up), I felt an electric jolt of pain in my lower back that forced me to immediately set the bar on the safeties and crawl out (not walk) from the squat rack. I was in so much pain that I couldn't even stand up. As I sat on the ground beside the squat rack, I started to sweat and feel lightheaded, then I actually passed out briefly. Woke up staring at the ceiling and couldn't remember where I was for a few seconds.

For the next day or two, the lower back pain was so bad that I could barely shuffle to the bathroom; even rolling over in bed was a slow and painful process. But the pain has been getting steadily better, and now -- a mere two weeks after the injury -- my back feels almost completely back to normal. Which kind of amazes me.

Anyhow, I'd like to resume training fairly soon, but I want to be smart about it. Although I want to squat since it's the cornerstone of Starting Strength, I'm kind of anxious about it since I don't understand exactly why I tweaked my back so badly on that warm-up squat. 115 lbs is not a heavy squat at all, and I was careful to take a deep breath and brace myself before each rep, so I thought my back was adequately protected. But obviously it wasn't. This is just speculation, but I'm guessing the problem was either that I went into lumbar flexion near the bottom (due to my noticeable anterior pelvic tilt), or I slightly good-morninged the squat due to letting the bar travel too far in front of my mid-foot. Either way, it's just scary to me how all it took was slightly sub-optimal form on a light 115-lb squat to tweak my lower back so badly that I passed out. Talk about walking on a razor's edge.

These are the things I've done, or plan to do (roughly in order of importance), before I resume squatting on my own:

• Contact a Starting Strength coach in my city (San Diego) for one or two in-person coaching sessions to really nail down my form
• Carefully re-read every page of the squat chapter of SSBBT3
• Re-watch Starting Strength tutorial videos on squatting
• Buy a pair of squat shoes with inclined heels to make it easier to achieve depth with less lumbar flexion
• Buy a lifting belt and possibly use it on all of my squats, even all warm-ups
• Regularly take video of my squats using an app such as Iron Path to track the bar path and make sure it's as vertical as possible
• Try to reduce my anterior pelvic tilt by doing exercises such as the butterfly stretch and third-world squat

I may be over-analyzing this, but I do not want to tweak my back like that again. Not my idea of fun. Anyhow, does this sound like a reasonable plan? Any other suggestions or corrections?