Two thoughts - are your legs the same length? My right is 1/2" (12mm) shorter. I was clueless until well into my 50s. And many of us find rotating the seat a degree or two to the side improves comfort a lot. (Most men who do this rotate their seatpost to the left. I go about 7mm to the left on my bikes.

If one leg is shorter, next question is uniformly? Ie both thigh and calf? Or more in just one of those. For uniform differences, like your entire right leg is a copy of the left only scaled (say) 97%, an insole or plate shim over the shorter leg's cleat of 1/2 the leg length difference works really well. I wear 1/2" lifts in my right shoe heels and 1/4" plate over my right cleats.

I don't sit upright enough for seatbone contact to be a big issue so I cannot help you there.

Edit: sorry, I didn't read your post very carefully. Sounds like leg length is an issue for you. Get that sorted first. Learn you leg length difference and whether that difference is uniform. Get the numbers so you can talk to others beside your fitter. (Fitters, even the best, come and go. You are stuck with that body for the long run.)