As a parent and a psychologist, I would explore all options that are afforded to my child to help enhance his/her skills if a language delay was noticed and a possible developmental syndrome was tentatively diagnosed. Especially, if difficulties have been evaluated by a doctor, school early intervention team or another agency who help children and families. Please consider contacting your local school district if you have not already to help guide you and your son.
You should check in your area for a Childrens Development Center. They specialize with children who have many different needs along with the pre school setting. The one my son went to had 50% of the class of children on target (w/o special needs). They offered speech therapy, OT, CT, and PT. They had plans for each EC student that included goals set by the school, teacher and the parents. The EC students had a wide variety of needs. My son has a chromosome duplication (dup.15q11.2) and mild CP. He made wonderful progress. I enrolled him at 1yr old. It was a long hard road (still hard but different) but he has made soo much progress. Several of his doctors are shocked at how well he is doing. He is now 8 and trying hard to keep up with kids his own age. I know that his school and the people in it helped him to be able to progress as far as he has.
Have you challenged him to talking to you to get what he wants? Ask the doctor? Speech therapy? He obsiously is very smart knowing his abc and numbers... Some preschools say they are positive reinforcement.. But they single out kids that age and they only know (not the day of the week) But at that moment. So if their discipline is time out then they don't get a reward at the end of the week.. That is double punishment.. Which isn't fair to your child.