Relax Thumb, Come Through Ball
Don't try to over lift or turn the ball during the release. It will only cause muscling and misdirection of your arm swing. Instead just relax your thumb and come cleanly through the ball as you release it and follow through, keeping your eyes focused on your target. For a strong release you need good lower body leverage (legs) and you also need to finish up close to the foul line . . .
Above all else, mentally fix your release point and stick to it.
Update: Here's a version with sound.