But see, even the math on that isn't adding up for me. Kaija is about the same age as the MC, and her skill levels (for combat, driving etc) are off the charts - like a global elite level. You don't do that with a two year community college degree.
I used to have neighbors whose daughter wanted to be an Olympic figure skater. From early childhood she trained probably 6 hours / day on average + school. (She didn't make it, fwiw.) To get to the level she's at Kajia would have had to start training in early childhood. So, I'm assuming to get to her current skill level she's been in training - for many hours / day since before she and MC knew each other, or at least as long as they've known each other. Which would mean that she has known all along about the Templars, and about his parents and has been hiding a significant part of her life from her "best friend" the whole time.
Is it possible that the Templars didn't kill Finn? Sure, but unless I have evidence to support that, I'm going to take Medb's word and assume that they did.
Does it matter to me if Finn tried to kill Kajia first, and died in the attempt? No.
If I found that they didn't kill Finn would it make a difference? It would probably be the difference between me never wanting to speak to any of them again, for any reason and wanting to kill them all. But I would still offer to serve Medb in whatever capacity she needed me to. If she says yes, then I'm back to killing Templars. If she says no, then I go home and hang out with Fiona - Talking to Rebecca (alone, on her own, and not in Templar HQ) is the closest I'd get to talking to the Templars and I wouldn't even give Rebecca any information the Templars might be able to use against the Elves. I'd just tell her that the Templars are completely lying about them, and they are just trying to protect themselves from the Templars and who are bad.