Could he just not be ready? He is only 3.5yrs right?
I have worked in Kindergarten and there are a LOT of kids that have no concept of letters and numbers. That don't have the ability to cut and write yet. There is nothing wrong with them...they just aren't there yet.
I would think as long as you are providing the opportunity for all these skills he will get it in due time. It may not be until after he starts kindergarten but you have laid the foundation.