M.R.
What ever you have to do, you should get your own evaluation of your son by a Developmental Pediatrican and own it. EI therapists are not qualified to rule out a medical diagnosis, and neither are private speech therapists. While these are terrific members of intervention teams, they are not first line diagnosticians, and without a full evaluation, diagnosis, and treatment plan, you are stabbing in the dark.
Call the closest childrens hospital and make an appointment with a Developmental pediatricain, use any and all insurance benefits you have, or find a way to pay for more speech and OTO over the summer, and get a master plan from a medical doctor who will tell you everything your son needs and is qualified to make the call on what he does and does not have. Then, use state and school services all you can, but you provide everything else he needs to meet the master plan from the Developmental Pediatrician. The state has no interest in maximizing your son's potential, they are NOT required to do so, they are only legally required to make your son "functional" which is a very low bar to jump. You want so much more than that for him.
Any EI therapist who suggested to you that your son did not have a specific diagnosis actually obligated the state to do the testing for that very thing. The school district should pick up from here in the fall, but don't count on them to tell you what you son needs. You should hold his diagnosis and you should never know less about your son than they do.
After you make the appointment with a Developmental Pediatrician, go to www.wrightslaw.com and start learning about advocacy. You will need to know how to navigate the school system so that you can get as much for him from public services as possible and preserve more of your private coverage for the rest of his treatment. You will always need to supplement his service if you want him to reach his maximum potential.
M.