disclaimer - I'm still learning. That said:
It looks like you're not on the inside, but rather are starting on the outside and bringing your wrist over the top of the ball. In almost all of my 10 releases, the rotation comes from the hand starting underneath the ball, with the fingers "below the equator" and letting the ball drop off the fingers. The way you're throwing it, your ball will not rotate if you just let it drop, since your hand is on top of the ball, and therefore you give it a little oomph with your hand. Which is fine, if that's what you want to do. I use this shot as one of my 10 varieties, and call it the limp-wristed over-the-top with a flip (seriously - I name all my releases).
Try just keeping the ball in front of your hand, your fingers down as low as possible, and just let the ball drop off your fingers after the thumb exits. the angle of your wrist to the foul line while the ball drops off will determine the angle of rotation (I call this release the "drop-off", of course).
To build up strength in the wrist, if necessary, use kettlebells (no, I don't own stock - there are several brands).
check out Slowinski at Slowinski
Here's the article on the release: The "Drop-off" release
"If it ain't workin', you're either throwing the ball wrong or throwing the wrong ball."
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