ABA works well for some families but not for all, manish- it has to suit the family dynamic. Would be a complete failure in my house and home, DIR works better inasmuch as we can manage a program or anything of.
Please Op don't feel you got it wrong, you didn't. it took me ages to realise ds4 was heading down the ASD path- despite 2 already diagnosed with autism and at that point being midway through an MA in Autism. Even now I am fully aware my professional head is not my mum head, it just isn't, people sometimes find it hard to give me advice but actually, I nee it as much as anyone because you don't see your own family as you do other children. You know, in my last job I had to arrange ASD training for volunteers and staff: I did all the research, met with the providers (a disability charity),..... and sat there open mouthed as they described ds1.
As for schools- gut instinct every time. Visit and ask about (I learned more about provision in 2 weeks attending a special needs sports club than I ever had from the LA). We currently use 4 different schools- 2 MS, 2 SN- but it's what is right for them and worth the organisational hell and spreadsheets it involves. And hugs to you, it's a bloody hard time, diagnosis. But time does help you come to terms with it, find ways of coping, and our kids can develop in ways we never thought imaginable. DS3 won't ever be fully independent, but he now chats away and could not aged 6, and can read and write even if not the same level as his peers. We just didn't think it could happen.