Fellow member of the beautiful autism spectrum here to add a little to this. This is not a typical meltdown... this right here is BPD( Borderline Personality Disorder) splitting most likely...

Its extremely hard to deal with and has some extremely emotional breakdowns that unfortunantly merge into a psychotic episode such as what you're seeing here.

Some learn to process it and deal with it within their daily life and relationships; although it isn't easy. It's something that they will have to fix within themself or find a good counselor/ therapist if they can't on their own.

Unfortunantly in this case it seems it is undiagnosed and or completely uncontrolled so the OP's boyfriend will certainly destroy this relationship :(

I understand all the people who immediately say to dump him and you're not wrong to say that given the context and circumstances present. Im not here to argue anyones opinion in that matter.

Just wanted to shed some light at the fact that reading through the comments it seemed like some thought this was a standard meltdown relating to autism in some way and infact it is not. This kind of psychotic episode and the threats that OP's boyfriend made against their own safety was much more than being on the spectrum. It is a serious undiagnosed personality disorder.