I agree you should get this moved to the SEN board. Mood management using various techniques is required to keep things on an even keel and avoid meltdowns as much as possible.
Telling off is not effective. Shouting, swearing, using brute force against a 6 year old child and throwing them anywhere sufficient to cause physical injury is awful. My ex used to lose his temper and regretted his actions but didn’t know how else to behave in the heat of the moment so would also hope/wish our son was not autistic so he was never in that situation. You both need to be on the same page and be willing to acquire skills of behaviour management so you can be the parenting team DS needs.
It might be useful to imagine DS was in the care of teachers or carers and experienced a meltdown that led to the same behaviour - would you expect more of them? Would you consider your husband’s reaction to be reasonable for them in those circumstances? Would just throwing him (anywhere) and ‘rough handling’ be acceptable?
You know this is not acceptable. You don’t want to ignore it. If it were a school you would move him. To make sure it never happened again if the staff member was not removed but simply retrained.
You should not feel guilty. Parent’s get overwhelmed. If there are 2 parents a tag team approach can be invaluable. But only if you trust your partner not to make things worse.
your husband made things worse and now that he has done so is claiming that his behaviour is your fault because the only reason that your not ok with it is because you ‘have anxiety’. It’s perfectly normal to feel anxious that your partner lacks the skills to deal with your child without shouting, swearing and causing injury and cannot deal with the fact they may have to acquire advanced parenting skills if their child has additional needs.
I hope your DH comprehends how badly he has fucked up and steps up. My ex is an ex because he couldn’t make the grade. Just too selfish and lazy to be good enough which required hard work and selflessness.