You are getting good advise here. not sure if you are doing it, but during your cheating tests you need to be shooting at your max flash power. that's where the duration is the longest. lower power will get you a bit more speed due to the faster duration, but then that would defeat the purpose. two other things though. from the look of the pics he is using the http://www.ryanbrenizer.com/category/brenizer-method/
to get that small DOF. personally, i like to refer to it as "my" method, as i thought it up a few years ago, long before i ever heard of anyone actually doing it, and that a dude has his name attached to it. in the end, i don't think it's all that great anyway, but that's another story. last thing- to help eek a bit more speed there is one other trick i know. now this is yoda stuff, so don't go around telling anyone, but since it's just you and me, here you go. sometimes you can hold your camera upside down. the black shutter will be on the top of the frame, and it won't see the flash. BUT it will see ambient, and many times the area above the subject is the sky, so flash wasn't going to do anything there anyway.