I was thinking about what you said about DDLC and yeah you're right, there really aren't that many VN characters who are THAT self aware, it's actually one of my fav things to see in a VN. (a bit of espoir lore but when I played DDLC on my own i was completely home alone in the dead of night and Monika said my full government name and I actually had to walk away from my computer and stand in the hallway to recover. I LOVED that feeling and wanted Ashton to do the same thing)
I wanted Ashton to also kind of apologize for what he did because it was kind of "not cool". At the time he saw his "friends" as just other game characters but after watching the player's dates with them in Reboot, he sees them in a better light and feels guilty. It probably wouldn't be a happy ending if Ashton STAYED as yandere as he did and i love happy endings! (because the game that inspired him will probably NOT have a happy ending!)
Hmm canon things about the boys? This I have actually pondered about for fun!
One rule I tried to keep is that technically Ashton is the only yandere character and the only one who truly loves the Tester. The others either see them as a close friend, or platonic buddy (although Kadsey does develop a crush on them). Also there is only one tester in the story, so there wouldn't be multiple Ashton's out there. Kadsey is definitely in love with Ashton, the reason being Ashton doesn't treat Kadsey superficially, that is take his hyper-ness and cheerfulness for granted...like Ashino does. I think I hint at this but Ashton is very honest and blunt with Kadsey while Ashino is very shallow with Kadsey, but I think once he overcomes that Kadsey will hate him less (someday!)
Oh one of my favorite cannons is that Vincent and Ashton bond over thrift stores and macabre things, both love horror movies and spooky things.
Oh another of my favorite (head?)cannons is that both Ashton and Ashino love 80s anime but where Ashton loves the more horror stuff like Lily Cat and Akira, Ashino loves stuff like Ranma1/2 and Creamy Mami! Both "Ashtons" are similar but in different ways♥
Sorry if that's a lot, these boys literally live rent free in my head!