I think the thigh pieces should be as high up as is comfortable, that way less undersuit shows. I have a garter belt system to hang my thigh straps from and I have a strap in front almost lined up with the seam and one also on the sides. This keeps the thighs up and also prevents them from twisting. There are threads on here for the garter belt.
I'd move the bicep down closer to the crook of your elbow, but you will have to play with it so it doesn't pinch. You might need straps from the bicep to the forearm pieces, I use velcro inside each and a strip of black elastic with mating velcro on the ends to keep my forearm pieces in place.
Ab and cod looks fine where it is. As for mobility by trimming the back of the thighs, well, TK's aren't known for their mobility. I'd get everything else adjusted and squared away and then spend some time in the armor to decide if you want to trim anything.