We initially decided to have it be a pretty challenging game (in particular stage 3 and the boss fight) and leave it overtuned so that not to spend too much time on balance. We were actually as well out of time and assembled the stages together in the last hour of the jam. Initally there were plans to add extends as collectible items, but seeing as the timeline was coming up, I instead opted to add an extend when you clear a stage (up to 5), and to reset the number of lives to 3 if the player falls under that.
A lot of people have reported the same landing lag issue that you have, which I did not notice during testing initially (I worked on the player character movement almost exclusively). It just so happens that is because I made the landing animation cancellable with a jump, but not with normal movement... I will likely address that as well in a future update.
The British bag o' tea crouch was actually a planned feature, I am glad you liked it!