I can understand your frustration - unfortunately the problem isn't something I can actually fix. To answer a few of your questions though, I have patrons who use joiPlay, they tell me about their experiences and also how to use the app.
It was also through their efforts that I learned the real problem.
Games built in Ren'py 8.0+ aren't compatible with joiPlay. Whether this was purposeful or a mistake on Ren'py's part - I'm not sure. The reason games won't run normally once they hit a certain file size is also something beyond my control. Any non-certified (that is, a game slated for app store release) Android game with a file size of 2gb or more won't run on android phones - it's a built in security measure. Using joiPlay is one of the only way to circumvent that.
In short, the only way for this issue to be fixed is for A) Ren'py developers to acknowledge and fix it (if they can) or B) joi Play to release an update so that Ren'py 8+ version games are compatible. It's also worth noting that this issue isn't something unique to my work, many other games have been experiencing it as well. The only real solution is patience.
The irony is that i actually avoided updating to Ren'py 8+ because I wanted to avoid issues like this from the beginning. Clearly that didn't work out too well.