I think you are right that the primary argument of the case will be whether Drejka was in reasonable fear at the moment of firing. As far as the letter of the law is concerned, that's the pivotal issue.
I wonder if the prosecutor will want to and/or be allowed to discuss Drejka's motivations. Especially if his prior incidents are allowed into evidence, a strong case could be made that Drejka intended to provoke an incident. Maybe they won't state it so plainly, but try to shade him as a willing agent of conflict. While this may not be relevant to the exact letter of the law, the jury is comprised of people and this bit of background info could be the little push needed for any fence sitters.