This point you made about imbalance in leg muscles has just illuminated a possible source of my back pain that should have been obvious to me but I just attributed it to age. My left leg is weaker than my right due to knee surgery I had a decade ago. My muscles never fully recovered and now I have back/leg pain on my right side. I will have to look into correcting this and see how my pain progresses over time.
The way that all of those things are connected and propagate is not just some pseudo new age nonsense, they're very literally connected in mechanical chains. My shortened hamstrings caused my lower back to roll in at the bottom of my squats. Lengthening my hamstrings fixed my squat and my back.
I highly recommend you visit a well-reviewed physiotherapist. I have struggled with back pain for about 10 years, from a high-school football injury. Turns out, beyond the "injury", I have a really skewed pelvis, which is causing issues around my body including my back pain!
The complexity of human movement is fascinating the more you learn about it.
