Change directions more quickly at the top of your extension - I think moving your feet a little bit would instantly help that. That is, instead of allowing your toes to remain on the floor, pick up your entire foot and replace it aggressively on the floor flat. Don't lift them up anymore than necessary to move them into your squat stance and connect flat-footed.
That foot movement will probably also help with your balance problem in the bottom position by keeping your feet under you better.
Don't think of jumping per se - literally just lifting the feet. You can practice this with snatch balances, tall snatches and high-hang snatches to make it a little easier to focus on.
It may be that in the past when you've tried to pick up your feet, you've done it too soon. Follow through on the extension and move your feet as part of your movement under the bar - make sure it's occurring then and not as a part of your effort to elevate the bar.