I’m not sure how best to do this, but in talking about this, it’s probably important to explain, rather than defend, those actions. (If you treat breaking a rule as insignificant - no matter how crazy the rule is - you leave the AO wondering what will happen when your kid breaks a rule at their school, one which fits into their norms.) Your son should be ready to show growth from (and remorse?).
In interviews, particularly parent interviews (or statements), you can describe the current environment (citing the fighting, bullying, etc) as one of the reasons you are seeking a different environment.
Most AOs realize that kids mature. Most also understand that many kids are considering BS to change their environment - for any number of reasons.
As an aside, particularly when you get to the point of choosing from schools where you have acceptances, make sure you look at discipline policies. These vary enormously, both in terms of what is an infraction as well as in how many poor choices you can make before being shown the door. I don’t say this assuming your kid is more likely than any other to get in trouble, but because this is one of those things that catches a lot of families flat-footed. Given where you are now, you definitely don’t want to revisit this!