When I was your age I would contract with local farmers to fix sagging out buildings built on stone piers. First I would build temporary timber framing inside. Similar to what you did. Then slowly jack the building up, till it was about 6 to 8" off the piers. Then dig out full depth footers and pour walls. Once it was hard, then slowly set the building back down after it had hung about a week with come-a-longs and cross jacks pushing and pulling the walls back straight. Once it was down and secured, then remove all evidence of the re-work!
All in All, I really like the exposed beams and wood trim on your project garage!