ABA saved our son. He started showing symptoms at three and a half, and quickly regressed from normal development to non communication and troubling behaviours. We put a massively intensive programme in place - 6 hours a day, 6 days a week - for three years until he was able to attend a special needs placement at Smallwood Primary, with support. We fought long and hard with Wandsworth to get him statemented, but once that had been achieved, the borough not only paid for part of the ABA costs (about 50%) but he was supported throughout his education - even when part of that was outside Wandsworth. He has just turned 27, and was recently awarded a 2.1 Masters in Photography from Goldsmiths College. It's been a long hard road, but he is fantastic and we couldn't be more proud of him.
We were at the early development stage of ABA therapies and there may be other methods that I don't know about, but I cannot emphasise enough the importance of early intervention. My non-scientific impression is that the autistic brain starts to scramble its connections, and needs to be re-wired back to normal - almost like a stroke victim.
I really feel for you and hope you can get a clear diagnosis and find a route through this. Remember to care for yourself too, and I'm happy to expand on my experience if you need more details.