You may want to consider if you want to keep the acceleration increase/decrease as it is or if you want to start off at full speed and end at full stop. Some people just want extremely tight controls and not want to deal with momentum nowadays. Generally though, I find that quick acceleration and break are best.

It's hard to give specific values without knowing what the flow of your game will be like. It should be as fast or as ponderous as the kind of experience you want to deliver.

Upon entering contact with any of the platforms mid-jump, I was able to reset the jumping and quadruple(!!) jump.

I liked the touch of the increased gravity on button release. It does remind me of older games I used to play involving hedgehogs and robots.

I didn't understand what coyote time(s) referred to.