Numb hands are a classic symptom of having your seat too far forward. Measuring with a plumb bob hanging from the nose of your saddle down, how far behind the center of your bottom bracket is it? It's important to have the two wheels on a level surface for an accurate measurement. Cement garage floors and driveways are often slanted to shed water. Depending on your height you might need several inches of setback. The idea is to balance on the bike by moving the saddle backwards so that your spine and legs carry your weight instead of your hands. The more aggressively aero your riding position is the further back your saddle will need to be. You can pretty much figure out it out by how it feels. Your ass tells you the best place.

If the bike is the right size and set up correctly and if you have the correct riding posture it should be possible to ride for hours without any significant discomfort of any kind. If you've ever broken one of your arms there might be length discrepancy between them. My guess is your saddle is still too far forward but another possibility is that your reach is too short and your bars are too high so that the bars are jack-hammering with some force against your hand. If so it might also cause your shoulders to hurt. If the reach is long and low enough there shouldn't be much weight on your hands and road vibrations won't be transferred up into your shoulders.