I don’t think I understand your objective. The AI getting launched away from the player when it was about to land on it is the solution to this problem which is enabled by default. Could you please explain what you want more clearly?
You can just redo that approach you didn’t like the outcome of but while their capsule components are overlapping, you can make it seem like the characters aren’t by playing a falling animation for the player when that happens. Or if that’s a first person game you can adjust the camera accordingly. This was my guess for a solution since I didn’t quite get what you want.
No 
I actually got a little bit confused. Here’s the correct syntax:
My point on having a stored variable is valid on timelines though. That was in fact where my mind went to. Btw you shouldn’t be using interps while you’re already using timelines. You can just use a float track and a lerp node.