Seconded here, frameset is a size too small. If you've got that many stack spacers and riser stem and upturned bars and the tips of the hoods are still just now getting even with the saddle..........frameset too small.
When you see things like drop bars rotated skywards and tips of saddles having the saddle with a reverse tilt.................fit/frameset problems.
Otherwise, in general some core strength goes a long way for how much weight is on the hands. Other thing is some folks ride stiff armed versus having flex in the arm. The arms being stiff/straight would mean shocks transmit into the hands more then into the neck/shoulders. Bent arms acting as shock absorbers will relieve both the hands and the neck/shoulders.