"But having the characters themselves talk about various items that might be useful doesn't seem very satisfying." One's own personal feelings should never get in the way of what's good for the game. What we grow accustomed/blind to as developers, for we know our own games the best, others may not know since they could have no possible way of knowing, naturally
"For the ending, I wanted to convey a sense of eternal limbo. But I understand that doing so just makes it seem like the game has stalled or something else is going on. I'll take that into account too!" That's fair, it just genuinely made me wonder if something's not working as intended or what's going on, did the game break or what? Putting in at least some kind of an ending-text would have been a better indicator, no matter how cheesy that would be
"each item was originally supposed to be an element of a more expansive lore that, due to time constraints, we weren't able to implement! So we did our best to include indicators to help you understand what to look for" That is fair, and I have no reason to believe otherwise
"(and originally there were supposed to be 4 of us doing it and not 3, another friend of mine who is actually trying his hand at level design)" I can relate to this with my own project of Hauntlings, that ended up being a revolving-door for programmers. My sympathies and condolences, friend
"also because I've never done Level Design!!" Considering that you've done a servicable job, well done!
This game has a lot of flavour and intrigue, and I could see this easily being able to be turned into a full release with slightly more elbow-grease