Part of what you responded to was me just inserting what his defense team might say. I don't have as many facts as his lawyer will have.
The culpability for me (young, strong) is higher than for a frail older person when it comes to self defense.
Many women have been aquited in murder trials because they felt intimidated by the person they shot, where if they were a young healthy man they would have likely been convicted.
I hate to say it, but I think this guy walks at the end of it.
By the way, not all theaters ban people who are otherwise allowed to carry from doing so. Most do, this one may, I'm not sure, but I don't think it has an impact on the legality of the shooting. A theatre that does not allow one to carry is simply trying to enforce company policy, it does not carry with it the weight of law.
The fact that this shooting was done in a theatre will have no relevant impact on the outcome of the case, notwithstanding any particular law Florida may have with regard to having guns in a theatre.