For right-handed controls: arrows to move, down to crouch, up both to hold rope and jump (but you need to add a delay otherwise it's impossible to jump from the rope), Ctrl to prone, Right shift to attack. Other controls can stay on C/V/B since we don't press them often.
I don't think 5) is needed but I don't see anything wrong with it and it would no longer require a delay to jump from rope, so maybe it's a good idea. The only issue would be when you want to jump down without holding the rope which I remember happened in a few levels.
I disagree with 2) and 4), for me the gameplay is very good right now, it just needs more enemies and maybe the first levels are a bit too long. Your new levels 15-21 are almost perfect for me gameplay-wise.
Regarding 3) I think you store too much information in the level files. It looks like every level contains all the game assets required to plqy the level, instead of simply defining all the assets in one file and then having only the level define the layout.
