jj, sorry I missed the pics. As King has stated, your spans are WAY TOO LONG..!! King is also correct that your middle finger is roughly 1/4" too long and your ring is close to 1/2" long.
I would shorten your middle by 1/4" and your ring by 7 1/16". This will leave you with a slightly dropped ring finger. This is how most of the pro's have their grip. Your actual span will be 4 9/16 for your middle finger and 4 1/2 for your ring.
Now as far as your thumb goes, you were dropping the ball because your span was too long, not because you had too much reverse pitch in your thumb. I would go with 1/16 left pitch in the thumb and 1/8 reverse.
Beveling the thumb is the most important factor in my book, not the pitches. The key is to get your thumb down in as deep as possible, while still being able to release the ball cleanly. You also want the hole tight. This can be done with tape once you've beveled the top of the hole correctly.
If you thumb joint is stiff, not like a hinge, then you'll probably need more reverse, especially if you want to put a high amount of revs on the ball.
Let's start from here and see how it goes. I'm sure it's going to feel MUCH better than what you have now. Good luck and report back. =:^D
