One sets the timeScale in Motion Page by dragging everything into place. For the reverse action an optional timeScale parameter could be implemented along the lines of https://greensock.com/forums/topic/20868-adding-timescale-to-reverse-only/
That way one could have the reverse play at a different speed.
For the second request. Maybe think about adding a “pause marker” for animations. As long as we don’t reach the marker the reverse plays backwards elese it plays until the end. See here
A seperate reverse easing would be quite cool, too. I know it’s cheesy, but sometimes ‘bounce’ has it’s uses. Bounce reverse on scroll exit is awful though. Would love to power out on scroll exit.