I think you need to completely reframe your thinking.
stop thinking ‘how do I punish him to change his behaviour’ and start thinking ‘how do I prevent him hitting out or having meltdowns’.
The approach you are taking is not giving him any support, empathy or teaching him skills on how to cope when he gets overwhelmed.
You should contact his school, local authority or local parent-carer group to see what autism parenting courses are available for you.
Read some books (The Explosive Child by Ross Greene is excellent), look at the National Autistic Society website. Find a therapist. Does he have an EHCP? What accommodations and support does he have at school? Has he had educational psychologist and occupational therapist assessments?
A lot of parenting an autistic child will look completely different from ‘traditional’ parenting methods.
The more you understand about his sensory needs, social communication difficulties, how to help him recognise and regulate his emotions, what his triggers are and when to spot him escalating the more you’ll be able to help him manage his difficulties.
For example WHY did he have a meltdown at his activity? Ask him what happened, what could be done differently then speak to whoever runs it and ask for adjustments.
Allow him time to do activities he finds calming, don’t overload with chores. Being at school, doing activities, anything social outside the home is exhausting for autistic people. Home needs to feel like a calm sanctuary where he can recharge.
Finally he’s going to be very hormonal, and there is evidence to show autistic people are more sensitive to hormones so while he’s going through puberty things are going to be more difficult. But the more you help and understand him the easier it will be for both of you.