Power Imbalance - Cramps and Periodisation

early last year and new to road biking (on a road bike) I tried structured training for the first time. I completed a 12 week block and saw a modest FTP improvement from 258-272, however, I had not yet heard of periodisation and each week was just as hard if not harder than the previous. Subsequently, I was worn out and ended up taking 10 weeks off the bike…
When I returned I treated myself to a new Wahoo Kickr Smart Trainer and immediately noticed that the Power Output was 13% higher than my single sided Pioneer PM. I now was not sure what FTP to use. Had my previous FTP gains actually peaked 300Watts FTP?
Not long after I installed a set of Dual Sided Favero Assioma Power Meters and found that I had a L/R Power imbalance of 55/45 - roughly 13% lower for my right leg.
Would this explain the debilitating cramps I seem to suffer at the 2 hours mark on a hard ride? I s my left leg simply pushing the right too hard?
What steps can I take to move towards a more even L/R Power Balance?
I’m assuming the imbalance is because of a motorcyle accident I suffered many years ago that resulted in a broken Femur…
I also suffer from a severe case of varicose veins on my right calf. - not sure if this contributes in anyway.
(43 year old Male)