Everything that has been said about bike fit is great advice and necessary, but for the numb fingers, it may be something as simple as the wrong gloves. Many bike gloves have padding that actually puts more pressure on the nerves of the hand than with out them. It is the same reason that a Brooks saddle does not need a cut out down the center, no padding to pressure the nerves. Simple test, do some rides without gloves and see if you are still getting numb fingers.
Greg