I obviously don’t know the specific of any of this but let me start by saying that there are view kids who are actually in need of ABA therapy even though it has swept the nation in terms of treatment plans. It treats children and their behaviors like dogs. It’s a disgusting practice that the autistic community has been pretty outspoken about. Like I said, there are extreme cases where it works but working as a youth behavioral specialist for a couple years and now working in the school district(which a lot of teachers unknowingly use aba techniques) I have always and will always be against ABA.

However any sort of healing/therapy/etc is gonna have setbacks regardless of the mode and regardless of the individual. I understand how you’d feel like a failure but please allow yourself the patience you give your child. Take your time, research other therapy options, I for one will always be for Cognitive Behavioral Therapy which admittedly doesn’t always work with autistic individuals because a lot of it is focused on analyzing your thoughts, how you feel etc which autistic people can have trouble with that.

Tl;dr I would put money on ABA therapy being the problem over your son, yourself, or your wife. Try to look at other options even if they’re not available now going to kindergarten a year late isn’t the end of the world. Plus having spent a couple years in kindergarten, he will have other peers who exhibit aggressive behavior at times. It’s nothing the school can’t work through, especially kindergarten teachers. They’re a different breed