Hey Rob, nice explanation of the different grips. There are few small things that I do differently which I wanted to share:
Forehand Power grip: I like to keep the ring and little finger pressing against the outside of the rim of the disc (you are actually gripping the disc like this in the video from time to time; e.g. 0:44).
Forehand split grip: if you want extra power on this grip, I would suggest putting two fingers inside the rim of the disc (your middle and ring finger) and have the little finger press against the outside of the rim.
Backhand power grip: accurate in my opinion, but seriously that middle finger isn't for balance right? ... It must be for a quick slipping someone the finger ;)
Backhand split grip: I completely agree that you shouldn't really use this because it makes angled throws (inside/outside) a lot harder.
Push pass: I find that the 'finger on the rim' method gives me a lot more spin and therefore stability. But I think you can throw further with the power grip. However, since length is not really the point of a push pass, go for the finger on the rim of the disc.