If he if doing this, and you have trouble with keeping him from destroying the house or hurting himself or others at four, you have to think about what the situation might look like when he is eight or twelve or older.

These are likely signs of poor frustration tolerance, perseveration, and difficulty with change- which are all signs of being on the autism spectrum, but maybe not.

If you are on a position where you don't actually need a referral from your GP for a pediatric neuropsych OR just plain old pediatric psych, to be honest I would just go straight on and make the appointment around the GP.

These kinds of behaviors at four, to this severity, are rarely about manipulation but more about a child pretty much losing it and having no clue what to do with what they are feeling. It kind of sounds like you know that, but sometimes we need to hear these things? I don't know.

But also- this really shouldn't wait. I know you don't want to go to the mhc and its very expensive to see a psychologist. In some states now a dx of an asd afford certain state benefits including state paid services but I don't know if you are one of those states.

I speak as a person who used to be that child,who would not have tantrums, but meltdowns of frustration to the point of passing out- literal physical exhaustion.
This is really important to address asap.

You are on the right track thinking that.
-Josie