This is a pretty good write-up that covers a lot of my thoughts as well. I debated with a friend over writing a similar comment in hopes it would be seen and some certain things about the game could be changed, but it seems I don't need to do it myself now. I'll also try to limit spoilers going forward, but I wanted to add my thoughts as well.
Password definitely has strong character development, but as you say, the weakness in some areas of the writing do hinder it somewhat. It can take too long and be wayyy too wordy at parts, going over the same exact things multiple times to the point where I would groan and wonder just how much longer this segment was going to continue. Day 10 was a big shift downwards for me, honestly, and the stuff after took what felt like forever. The payoff was good, though, and was a good moment. However, I do feel like my experience was lessened by picking Sal first. Some things just happen differently in a way that probably weakened the overall experience for me. In fact, the password I was supposed to have entered around that time was just outright spoiled later in the game even though I had never entered it, which I assume is an oversight that slipped through the cracks. In a game like this, that's bound to happen, so I can't be mad at it.
As you say, the overall mystery and delving into morphic resonance was pretty good, and it's easy to draw the lines between Password and the Zero Escape series (999). I just feel the need to echo my dissatisfaction with the "true" ending. It's a heavy black mark that honestly ruined the game for me and a friend. Path A is definitely the "better" ending but knowing what's out there and the time investment to complete it is... just such a bummer. The effect it has on the story and everything that happens... I don't want to go more into it because of spoilers, but I reeeeeallly hope this is revised in the final product. It's just so frustrating, but with all the respect towards the author and the story written. I say this with love because I grew to care about the game. (Also, #justiceforsal because he's honestly treated the worst in the game... I didn't even like him, I picked him as a middle choice, but man it kinda feels like the author didn't even like him either.) ((Also also that one bit with Tyson near the start is pretty bad too...))
I think that covers what I wanted to add/emphasize. Password is overall a fine game with some great character development that could just use some trimming and some revisions in places, namely the endings (Oh, and, the antagonistic force in the last third to fourth of the game, that all felt a bit rushed.)