“July 2020-Noticeable weakness in left leg, buckling sensation with exercise and walking not sure where it was coming from (knee or hip)”? You might not remember, but what buckled, the knee or hip (the knee would buckle if the hip hurt to protect it.
Neurology suggested it was a “stretch” injury from surgery and will take time”. What did the EMG specifically note? You noted; “A few weeks before surgery began using crutches and work discontinued due to left leg weakness, abnormal gait, and lower back pain”. If the symptoms did not substantially change after surgery, this would be an incorrect assumption.
“I can work restricted shifts with a stabilizing knee brace. I can use the elliptical machine and stationary bike, but it is difficult to keep weight in my heel. I am unable to walk with a “normal” gait, I cannot run or hike. When I stand, walk, or sit for an extended period my lower back aches with pain into my gluteal region. I have warmth and numbness in my left foot, hip, groin, and coccyx. If pain were the only issue, it would not restrict me from further activity. However, the weakness and abnormal gait does”. This indicates you don’t have pain inhibition weakness. When you walk, does your left hip drop when you weight your left leg (trendelenberg gait)?
“Dr. Colorado Pain Specialists 6/18/2021. Diagnostic nerve root block. Complete pain relief for four plus hours on the right side (desired effect)”. My understanding is you don’t have much pain and no pain inhibition but weakness especially of your knee as you wear a locking knee brace. If this is not a pain condition, be very careful using a pain injection as proof of “the problem”.
I would be exquisitely careful of having Tarlov cysts repaired. This is a direct surgical manipulation of the sequestered nerve roots and great malfunction can occur. I generally leave these cysts alone unless they are eroding the bone of the sacrum. I’m not convinced these cysts are causing your weakness.
I think a new consultation with a neurologist who performs the EMG him or herself would be your next step. Make sure this individual has great experience and is adapted to discovering rare disorders. There are many neurological disorders that need to be ruled out.