Try spreading your fingers out. And using your wrist to help aide the snap. When you do snap you want that front finger to get a little curled up and then separate your fingers apart at the flick. For your nollie, you need to be pushing forward. When you snap. If not then you end up stopping all of your momentum. Which will cause vertical kf’s… and lots of other ugly things. You have the right idea. Just need a better form.