OK, can I ask when it's happening? You mention him getting into a meltdown after school - does this happen a lot? Was there something that was very different about that school day, or was there something new he was having to face when he went home that evening? I'm wondering whether he's panicked because he was already totally exhausted and couldn't handle something new, for example?
Avoiding getting into this state is important for all of us on the autism spectrum (which I am as well). I know that I have to manage my energy levels very, very carefully, and manage how much input my brain is getting and for how long. Because my eyes and ears etc can take in three times more detail than other people's, and because I can't 'switch off' from any of it, ever, I get SO exhausted after a day in a noisy social place. It's like having to live and work in the front row of a Rock Concert.
For me, it causes me to 'shut down'. For many lads, it causes a meltdown.
Finding a quiet place to let our brain wiring calm down and cool down is so important for many of us. Is he having the chance to do this at school, for example?
What you're doing in letting him go into his room to calm down is a good thing.
No way should we be using violence or swearing, so he definitely has to learn to express his needs differently. Worth reading a bit by Dr Temple Grandin, who talks about the ways she learned to manage her anger, for example. Lots about her online or you can buy her books.
What support are you getting from specialists, professionals etc? They may have really good ideas to help get you all through this.
Have a cuppa...