I'm glad to hear that you have enjoyed improvement. I myself did not have that problem, although I always wondered if the occasional aches and pains that I got were related to the donation surgery. I quite agree that exercise, posture and healthful diet are always helpful. I started running after donation surgery to help with recovery and have continued now for 12 years, and I think it is a great help.
One possibility to keep in mind is "adhesions". The internal organs are naturally covered with a slimy substance to help them move against each other easily when we move. When the surgical instruments, or the hands of the surgeons, touch those surfaces that barrier can be disturbed. If two disturbed surfaces are touching each other a spider-web sort of scar tissue can form binding them together (an "adhesion"). It might be harmless, or it might put a kink in things and cause problems. They can be hard to identify, and surgery to correct them may end up causing new adhesions. (I'm not a medical professional, so I'm just passing along some info that someone else passed on to me.)
Please keep us informed about how you do, and about anything new you learn.
best wishes,
Fr. Pat