You can try adjusting the height on the pickups and lowering the bridge pickup will generally help. Try adjusting the single coil pickups closer to the strings. I always press the high and low string down at the last fret and adjust the pickups to about 1/8" on the bass side and 1/16" on the treble side. If the humbucker is still too loud then look for some after market replacement pickups. You can use stack pickups where the coils are on top of each other or try using single coil size humbuckers that have two small coils side by side. They can generally give you lots of output.