tjpowell -- You've received a ton of good suggestions from your fellow Speedliters. One suggestion for your test shots, also try them with the sun coming to the side of your subject and also over his shoulder towards you. There is not a lot of fill flash happening with the sun coming over your shoulder. Fill flash is best when the shadows are too dark/contrasty for the camera to record.
For the backlit shots, you will likely want to put the center circle of the viewfinder on your subject, push the Flash Expsoure Lock button (the * button), recompose the shot as you want to take it and fire (all within 16 seconds of hitting the FEL button). Hitting the FEL button meters the scene from the center circle rather than the whole frame. This is a big help with backlit scenes.
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Syl Arena
Speedliting.com