Yo! You are correct that I didn't really read any of the notes. I think I clicked the first New York one and found it a little wordy and decided I only wanted to click additional notes if it was for a concept I needed more context for. Often the notes were highlighted for subjects I already felt familiar with, so I was like "I know what that is" and didn't read them.
I was playing on Browser when I had that issue with the galaxy shader. Just to be thorough, I booted up the game just now on the downloadable Windows version, and didn't have any problem with it at all. (The animation would freeze briefly in between text boxes, but I don't think that was a performance issue). I don't know RenPy well enough to understand its limitations, but it could be worth looking into a way to check if the player is on browser, and reducing the animation accordingly. I would recommend waiting and seeing if other players report issues on browser as well before doing anything too drastic, but obviously having it completely freeze my computer is pretty major!
The text size problem was also simply because I was playing on browser, where the window is very small when I'm not full screened (and the only reason I wasn't full screened was to ensure I could access my control panel in the event of another freeze). When I played it briefly on the Windows version, the text size felt comfortable to me, but I didn't play enough to have a strong opinion on that front. If nobody else complained about it, then it's probably fine! Maybe a larger window on the Browser build would be appropriate though, if you're able to reasonably control that.
I really respect your philosophy on making this for yourself, and I am totally in that same boat with my own projects. Regardless, this is a very well made game and I hope it reaches its audience! I know I enjoyed it, at least!