Just drop it for a while.. The secret is to read to him.. Sometimes, follow the words with your finger. Then continue to read to him even while he is in school..
When you are driving around does he know the "Golden Arches" are an M? M is for McDonalds..
Does he know the first letter of his name? Does he know it if he sees it?
Also google "fine motor skills for young child".. Do them as activities. They are a lot of fun.. You will need some playdo, so he can roll out little balls of clay.. Then have him line them up.. then have him squish them with only his pointing finger on each hand.
Give him a whole box of big paperclips. Show him how yo make them into chains! How long can he make his chain?
Another time, give him a box of small paper clips.. Make little chains!
Have him drive his small cars only using his [pointer finger.. then only with his thumb.. You race him doing the same thing.. See who is the fastest.. have him do this with each hand.
All of this is fun to him.. but it is actually helping to strengthen his fingers and hand muscles..
Outside have him pour water from one container to another.. all sixes of items. tiny to great big..