I'm using MV so I'm not really familiar with scripts, but I know that common causes of errors are from scripts conflicting with each other, being in the wrong order, or being the wrong version. Testing things in blank projects usually helps, if there's a crash there, you can take a guess that there's something wrong with the script itself and seek help.

I think the puzzles do rely on the player having a certain level of background knowledge and patience to sit down and think. It might not be for your average player, but as long as they can actually be solved (have seen a game where only the dev would know the answers :S), I think people will still take it on. If you're worried about making the game accessible to more people, having a strategy guide/extra hints somewhere will help those who still want to play and just got themselves a little lost. My problem with the piano puzzle was after reading the sheet music, I headed to the piano thinking there'd be an input screen, but there was just a long pause and I thought it'd crashed. (Was I just supposed to type directly?)

Life drain I can take or leave. Not really sure if it was doing damage over time or just by the number of steps. I found it more annoying than intense, but I guess it was a means to an end in your story to make the player more interested in finding the solution and antidote. As I said, the atmosphere wasn't quite there for me. I was annoyed that the cat told me to 'get fucked' since I didn't feel it was very encouraging to try again. Of course there are some people who are fuelled by negativity and will take it as a challenge to fight and prove themselves, but I'm sensitive and prefer to be positively encouraged XD So the atmosphere not clicking with me is not a fault of the game, it was just a matter of personal preference.