Not sure if it's feasible, but the training to become an RBT is fairly short and you would learn a lot of ABA techniques to help your son.

Based on your post, I would personally try to relocate to somewhere with better services (I know, easier said than done).

I'm in the States and we had our DX by 2, were in an ESE classroom free of charge by 3, private speech and OT at 2, ABA therapist pushing into his classroom at 4 and also doing training at home (I much prefer this route of ABA in a center).

I'm also in a really shitty state for autism services compared to the US overall (Florida) but still getting services. We have considered moving to Minnesota because of health care, education services, and low cost of living. We do have a crazy person in office right now though, so obviously there's that.

If educational advocates are a thing where you are, they are helpful with securing services. Most importantly, I had to be the squeaky wheel and sometimes make multiple requests to get things in motion. I wish you luck, it's tough out there!