Great call to make this in Pico-8. It forces you to keep scope small so you have a higher chance of delivering a quality product.
Your level design is some of the best I've seen in this jam (I do not say this lightly as I've played roughly half the Mac-compatible games submitted so far; plus, I'm a perpetual student of level design and it's an easy thing to get wrong). Yours is laid out in a clean, well-composed way and I can see you put thought into your choices. You're difficulty curve is measured and intentional. You introduce challenges one at a time, giving the player time to understand how they work before mixing things up. You're using the Pico-8 frame-size limitations to tease exploration. Your lock-and-key progression is solid, often introducing the lock before I get the solution. Good choice to use narrative as a reward for exploration between power ups; this frees you from having to introduce more complexity through other kinds of gamist pickups. Nice mix of verticality keeping the level shapes fresh. Solid level metrics keep the space from ever feeling cramped and jumps feel good. Using houses and other unique sprites aid in mental mapping to keep players from getting lost. You've got this large enough to allow for exploration, but small enough that when combined with the previous point keep it navigable without constantly referring to the map (until mid-game). The biggest downfall is navigation during the mid-game. After the map really opens up in the second area, I did get stuck and was unsure how to progress. When you have this many tiny rooms and a map that doesn't give detail, it's difficult to remember where potential leads are for progressing.
Transitioning upwards with the wall jump is hard because you'll instantly teleport up out of the level, then fall right back down with no time to react. It's disorienting. Take a look at how Celeste tackles this problem. Platform edges immediately after transitioning into a new screen are also harsh; you can possibly solve this by disabling input for a brief moment after transition to give the player's brain enough time to process.
I sincerely hope you're proud of of your work. There's good stuff here.