Ok here is the complete Dylan timeline I made. A labor of loathing
Day 17: One of 12 guys to enter. He gets to stay when 6 get dumped immediately.
Day 20: Kenzie chooses to couple up with him.
Day 22?(maybe 21): Kenzie has a conversation with and then makes out with Gal. She tells Dylan about it. He cries. She's surprised and feels bad. She says her conversation helped give her clarity on her feelings about Dylan. The next day they decide they're not exploring and will stick with each other.
Day 23: Movie Night. Among other videos we see Kenzie and the way she handled the Corbin/Caleb situation. Dylan expresses that seeing these clips is hurtful and shocking because it's like what just happened with him and Gal and Kenzie.
These clips mostly take place from days 10-13. Which were days that multiple Casa people specifically Titi, Amora, Carl, Ronnie, and Corey all expressed having seen the events of from watching the show. Making it very likely Dylan ALSO saw these clips from watching the show. Which makes his reaction when Kenzie tells him she kissed Gal and during movie night very suspect to me.
Day 26: They win the karaoke contest which saves them from being in the bottom 3. Afterward Dylan says he feels good about being there still. He feels confident where they're at. He's excited.
Day 27: Dylan starts worrying to Carl about why they were in the bottom 3. Is America seeing something that I'm not? Is this behavior a pattern with Kenzie? He feels like he put a lot of work to keep this relationship going. Later on Carl tells Kenzie a small part of this and tells her to talk to Dylan.
Kenzie and Dylan talk, take a break for advice from their councils, then talk again. Dylan talks more about patterns, asks how is he supposed to trust what she says. Kenzie says she really likes him, and wants to build something with him. But how can they build anything without trust. If he doesn't believe anything she tells him then this is not going to work.
TL;DR They meet and flirt and explore and 5 days later she kisses Gal and tells Dylan about it and he immediately cries. They agree to be closed off. 5 days later they are in the bottom 3 of the vote, and this makes Dylan worried that America is seeing something he doesn't and he can't trust her. Kenzie says she wants to be with him but if he can't trust her maybe this isn't going to work.