So he's 2 1/2 years old. You say he's been to Head Start/Birth to Three? Does that mean that he's had the evaluation for special services? If they did an informal evaluation that doesn't count. You need to make a formal request in writing that they perform a formal neuro-psych evaluation. You requested ... something, I don't know what since you're being somewhat vague ... with them but you didn't get any answers. Something told you, your Mom Instinct, to get them to help you for early intervention.
If you have insurance, you need to find specialists in your network that you can be referred to by the pediatrician. I'd be curious to know what the pediatrician thinks about his social and cognitive development, and if the pediatrician thinks he has global delays. Anyway, you can request to be referred to a Developmental-Behavioral Pediatrician; Pediatric Neurologist; or a Child Psychiatrist. Any are qualified to evaluate your son.
It's not too early. He's at exactly the right age. Early intervention, if he needs it, would be valuable right now. The reason I'm suggesting an independent evaluation is because if there's something that comes up with it, if there's a diagnosis or diagnoses involved, then that trumps whatever the Early Intervention people say and they must take notice. A formal diagnosis would legally entitle your son under IDEA to special services and they can not then refuse a formal evaluation (if that's what happened).
I'm guessing that you're suspecting that your son may fall somewhere on the Autism Spectrum based on the signs you shared but it could easily be something else or it could just be that he really is developing at his own pace (and maybe needs a little help and nothing else). I would make a list in a journal about how he's been regarding each of his milestones through babyhood to now.
Check this link out and see if any of this sounds like your son. My 11 year old daughter has ASD, and hits a majority of the traits but misses the boat on some. Some of the traits she has are minor, some major, some are occasional, some infrequent, some rare, some moderate.
http://www.autism-society.org/about-autism/diagnosis/dsm-...