When I read Tory's text message, it didn't seem to me like he was apologizing about anything related to Kelsey or even Kylie. If we follow the chain of events as you see them, Kelsey shoots first, Tory gains possession of the weapon and shoots, by this point in time Meg is shot and two people have fired a weapon.
Furthermore, there's no reason for Tory to apologize to Meg for sleeping with Kelsey when he was literally fukking Kelsey first and Meg is the one that told her to pursue him. Meg is the one that fukked Tory behind Kelsey's back, not the other way around.
You really believe after that chain of events, he's texting to apologize about Kylie, AFTER Meg has been shot?
Seems like Kylie would be the last thing she'd be concerned about... after being shot. Also seems fair to say that he was sober when sending these messages fwiw
We can even ignore Meg's caption here.