I think violence does become an "addictive" for want of a better word, way of releasing stress and anger and getting attention.
Keeping calm and reducing pressure CAN go hand in hand with boundaries if the boundaries aren't reactive. ie if you tell someone that certain behaviour is unacceptable that is a reactive boundary, whereas if you create a timetable which is very simple and structured or give a very simple task or chore at the same time every day that might make him feel safe.
13 year olds are very difficult at the best of times whether they have ASD or not, they tend to have loud outbursts and impulsive behaviours, added to which they are hyper sensitive about perceived insults or restrictions. Even a NT teen will appear to have absolutely nil empathy with their parents's feelings at times. However that is not to say that very violent behaviour is something you have to put up with or accept = I feel that you have to redouble your efforts to find what is setting him off, why certain tiny things might trigger him and what is the context.
These things have helped ds2 (and my NT dd) Knowing I am on their side, this is what I try and reinforce when they are in a good mood. Joking and laughing with them when they are in a good mood. Sharing things when they are in a good mood ie watch favourite telly progs with them, chat about somethign that interests them however dull.
Exercise. Ds2 runs 5k race every Sat. He walks a lot. He is not naturally sporty so this has to be worked on. Lots of medals, reinforcers ( he likes tubes and cafes as end goal, hates country walks) Dd does a dance class on Sats.
One chore that is his. Ds empties recycling. Work with OT has also helped clarify some issues with ds about goals ie getting ready himself, ownership of some simple life skills. I laid out his clothes and zip card(travel card) for a long time though, it is worth reducing stress for sake of getting other independence stuff off the ground (ie getting out of house, getting to school calmly, activites etc)
Things that restore and relax to reduce anxiety. Cats in our house, familiar fun things (Red Dwarf, football on telly, a few friends, even one will do, to come round and do familiar activity (friend is something that needs a lot of work but makes such a big difference to help them make one and encourage them to come round - so important when you are 13 to have a peer you can relate to)
I noticed that now when ds2 is angry he tends to focus on something less serious, ie he shouts rather than hits or he complains rather than seeking to do something vindictive. It is as if he has found other ways to express his emotions - still not good of course, but much better than violence or revenge. He has also started to notice when other people get angry and emotional and suggests they calm down or find other solutions, he is seeing anxiety for what it is and how to help deal with it. He is nearly 15 now. His worst anger was about 11/12 and in his case it was about social isolation and homework.