Legitimate resolve to fight Luffy the next 10 minutes properly, but betray the WG/Gorosei and possibly sacrifice himself to allow Bonney and group to escape once he hears VPs message.
I entirely believe the message is what is going to send him over the edge.
It's pretty clear to me that Borsalino has been going through an internal conflict this whole arc. Seen the "Go" he said to Doll and that he finally killed Vegapunk (allegedly) it seems he made up his mind, but hell he still strikes me as someone who's not fighting with the heart in it. And the continuous close ups of Kizaru's face are Oda's way to make us perceive that, imo.
I agree with you: Kizaru is being written as an intentionally controversial and tragic character. I think he'll
really make up his mind at the end of the message and do some kind of sacrifice to make sure Bonney escapes safely. And MAYBE he'll drag Saturn down with him.
He really is and interesting character, which I didn't expect before Egghead Arc.