I'm not sure what was happening with the jump on your end; the gravity scale is indeed higher on the way down (to avoid a floaty jump), but not so much that it feels particularly crazy to me. Perhaps not having a terminal velocity is the culprit? Or perhaps you're not used to variable jump height in platformers (i.e. that releasing the jump key sets Y velocity to zero)?
Controls are always difficult to perfect for me; I can see where you're coming from with the awkward hand position. I just hate pinky-based buttons, so didn't want to use Shift or expand the ZXC to include a fourth pointer finger, but perhaps that would have been better. For interest and my future control schemes, what button setup for the keyboard would you have preferred? (The game also supports controllers, which may feel better?)
As for visuals, we like the style we ended up with here a lot, but I understand it's impossible to meet everyone's tastes. The stretched sprites are an unfortunate side-effect of trying to triage the remaining outstanding art assets in the last couple of days of the jam.
Thanks for playing and for the extensive feedback. I'm glad you enjoyed some of it at least.