Is your son attending preschool in an Early Childhood program? He should have an IEP to specifically set goals for all areas of his development. If he is not, contact your school district administration tomorrow and request that your son be evaluated for the Early Childhood preschool program in your district. Really -- call tomorrow.
If you are getting therapy through the school district, you may want to consider additional (private) therapists for your son.
It's so important for you to talk with his current therapists and have them set concrete goals for him. Tell them exactly what you hope he will be able to do...and see what they say. Find out what they believe he is capable of right now...and what is realistic to expect in the next 6 months and next year.
The most important thing you can do for your son (after loving him!) is to become his Advocate. If you are not seeing results from his therapy -- address it. Explore the different types of therapies (Floor-time, ABA, etc.) and pick one that sounds like it fits you and your son. Ask your therapists to teach you how to help continue his learnings at home. They will have a million play-based ideas.
Unfortunately, and very sadly, there is no single way to solve this problem and "break your son from this shell." With the right therapists, the right therapies and the right early childhood cirriculum, he will make progress and can learn some, if not all, of the things you want him to do. You need to work hard to get your son what he needs...even though no one will exactly know what he needs.
I'm sorry you are going through this. Please try to find a support group in your area for parents of children with Autism Spectrum Disorder. They will give you SO much excellent information (and will know the best and worst therapists in the area!)
ETA -- If your son is 3, he is no longer eligible for Early Intervention programs. After a child turns 3, services are provided by the school district via Early Childhood program. That's why you need to contact your School District Administration.