Re: Do you test like this?
Sure, a live off arm is best - the punch should always be ready, even if it isn't delivered. And yes, regardless of speed, body position, connection, posture, etc. should always be as good as possible.
I didn't watch enough of the video to really comment on how open nage was - and besides, I think it's a little hard to tell some of that from a video anyway. If I could take ukemi for him, I could give you a much more informed opinion.
With Jim, Pat, and the others in Cleveland you are in good hands as you go along towards shodan. They will spot your openings and help you correct them.
And by the way, you can ask to see Jim attack somebody else, but don't be surprised if he just laughs and attacks you too!