Thanks! I'm really glad that you like my theory!
Also I'm new to the comments section for itch.io as well, so I've been trying my best to learn how it works.
Honestly I adore Route 65, as it is what made me like Chase (mainly cause he seems like such a literary nerd in Route 65). It is interesting how it acts as a branching point for what happens to the group as they move forward towards Echo.
I like the idea of what 'really' happened with the group of friends. This theory kinda reminds me of the difference between Higurashi no Naku Koro ni (Higurashi) versus Umineko no Naku Koro ni (Umineko), both are great horror games by the way. These are both stories that appear to loop, however, the cause of the loop and if they actually looped is different. Higurashi repeats the summer of 1983 over and over again and the goal of one the characters is to stop the loop they are stuck in. All loops are equally likely, but they are looking for the 'best' loop where everyone gets a happy ending. Umineko on the other hand shows a series of events in early October of 1986, with two characters arguing over if what happened was due to the supernatural or not. What is interesting about Umineko is that another character joins later from the future, which means there was a definitive set of events that happened and its up to the audience to deduce it based on what they are shown in all the loops.
I think your theory is another good way to look at the story, especially as an alternate to the branching timeline theory I posed. There are some things that are consistent in multiple routes and it brings up the question of why? For example, Duke is found dead in Chase's car in both Leo and Flynn's routes, but SPOILERS [Duke is alive and still an asshole in Arches Build 3].
If we look at it with the one true set of events theory, then Duke being found dead in Chase's car could not have happened. We are also then able to deduce the epilogues for Leo, TJ and Flynn's routes are not part of the true set of events, but aspects of each might be. For example, we see that Kudzu and Micha exists still in town, outside of their respective routes (seen in Flynn's route) so they are a part of the true set of events though it may be different from what we have seen. Another example is that Flynn's aunt is killed in Flynn's route and hinted to have died in Jenna's, plus Leo's route mentions a body count of about 9 people (Likely including Mayor Moore). We also see Duke always tries to accuse Chase of being the cause of the Hysteria in every route (aside from TJ's where the Hysteria doesn't fully set in), so we can assume that Duke definitely targeted Chase.
I think it is fun to look at the game through both theories. The branching timeline theory helps to explain some of the issues/differences that occur between routes, while the one true route theory can be used to deduce what would occur in all routes (even when we are not shown them on that route). At the end of the day, my theory is just that, a theory, so your ideas have just as much weight.
Also I highly recommend Arches and TSR now as they both have been fun to play through with what is currently there, but I understand the preference to wait till its finished.