My forearms get a little sore from twisting the throttle and shifting after 6-8 hours of riding in the hills, but I get no wrist pain. From your avatar I assume you ride a cruiser with high bars so the wrist pain is not from putting weight on your wrists while you ride. Can’t comment on your pre-existing carpal tunnel. One thing to try is to adjust the angle of the brake and shift levers, so when you squeeze on the levers, your wrists are at a natural angle. More often than not, the lever angles are off for a new owner. Second is to relax your grips. Wrap your hands around the grips very loosely, like your holding canaries – don’t want them to fly away, but don’t want to squeeze and hurt them either.
About stalling when taking off from a stop, try giving it more throttle, and slipping the clutch more. Beginners tend to let out the clutch too quickly, and not give it enough throttle (afraid the bike will jump up to speed too quickly) -> the bike stalls. Instead, give it more throttle, but let out the clutch much, much slower. How quickly/slowly you let out the clutch controls how fast/slow you take off from a stop.