It’s been a while since I’ve read Summer Reign and I wont be able to answer all of your questions. I forget what sparked the confrontation but I believe it escalated because Declan was blindsided by the fact that Chris’ unique aura can shred through magic. So he was reacting on base instinct rather than actively thinking about what he was doing. I think everyone is concerned about the amount of power Declan can wield considering his age. Not to even considering his relationship with Omega. So whenever he acts even a little bit off the response will be huge.
Aaaaand it’s time to re-read the series for the umpteenth time! xD