Wow, thank you so much for the in-depth answer! Sorry for the long delay in response, a game I wrote a soundtrack for just released on Steam and I've been working closely with the developer to make the launch go as smoothly as possible.
Several of the issues you brought up are being addressed in an upcoming patch - great catch on these though. The hitboxes have long been an issue with that perspective and I am enlarging them in the next update to deal with that. Feats are obtained by spending Feat Points - so you didn't miss out on that 40-point Feat, you'd just be able to spend the few points you started with on an equally small Feat.
The slimy lever is indeed used - but it requires some investigative work to complete the puzzle. ;)
I really appreciate that you took the time to read the dialogue and lore of the game - I put a significant amount of time into it!
And as for the other issues, I've taken note of those. I'm really glad to hear that you had fun playing!