Welp, after getting up the right side, realizing I didn't know how to get to the lever, doing one of the left side ones, and struggling with key+flip for a while, I reset my save data to check if the cracked blocks from the "ending" were a hint to something in the intro. They weren't, and save data reset is irreversible (as advertised). Not really mad, I kinda did it to myself, but I think I'm done for now. Maybe I'll try again in a few years lol
Thanks for the encouragement. In general I prefer to figure all these things out on my own, but I'm sure I already partly spoiled what you're talking about by scrolling too far down in the comments anyway. Guess I just ran out of patience, but like I said I'm not mad.
In terms of how long it'll take me to get around to trying again, if ever, you can blame pathological demand avoidance for me simply not wanting to do things on anyone's time frame including my own. This game will probably be preserved for most of the rest of my life, so there's a decent chance I'll revisit it eventually, but my main obsessions right now are quite unrelated.