Hello young doctor of the future, how nicely you have described everything.
Two things you haven't mentioned, do you get more pain on bending forwards or backwards, and do either produce a tightness or pain in one leg, compared to the other?
What's good is that these pains go spontaneously over, what's not good is that you are getting symptoms in both legs.
That numbness on the side of the thigh could well be Meralgia Paresthetica, a double pinch in the groin and facet syndrome in the upper lumbar spine. Press just medial to the ASIS and distally - any discomfort?
At the back of the other leg fits with a S1 sciatica.
Personally, I'm not much in favour of extension exercises, they quite often aggravate, and mostly we are weak in the abs.
Mostly I don't fuss over non-painful clicking sounds from joints, but perhaps in retrospect it was a warning that something was lying in wait. That's all set in concrete though, and you're looking to the future.
At C-H, you'll see a Search this site: "Lower back exercises." Every clinician has his/her favourite exercises, these are mine. I do them myself. They shouldn't cause pain or discomfort.
I'd start rather with walking and perhaps swimming, and cycling is usually okay, but be careful getting on and off. When you can do those without pain, then start jogging.
Sounds to me like it's time you started looking for a reputable chiropractor in your town! Take your scans... of course, I'm biased, but I and I presume all chiros treat these complaints on a daily basis.
Loss of the lordosis is usually caused by muscle spasm, but research shows muscle relaxants are ineffective.
Sitting is hard on the lower back, and yes it may inhibit you as a dentist, but you can get up between patients and walk around, even lie down and do two minutes of back exercises. Few of us are in perfect health...
Good luck, and I hope this has contributed. If you're half as good at understanding what is going on in mouth, as in your back, you have a great future!
One little tip: try and not take wisdoms out under GA in the future. Can cause havoc with the TMJs. Better in the chair.
Dr. Barrie Lewis