Chris, in the video above from your YouTube site you display using structure and alignment to resist a push on your outstretched arm. I noticed that your arm is stretched out to the side so that you are taking the push laterally. Have you tried this exercise with your arm stretched out in front of you so that you are taking the push head on instead of from the side?
You can try this with your feet in three different configurations: in a right or left stance, natural stance with feet parallel, on one foot. You can also vary the configuration of the arm being pushed from ramrod straight to having wrist, elbow and shoulder configured as in diagram 1 of your alignment series. If you give this a try I'd be interested in hearing about your experience.
I've done all of these things quite a lot. With feel parallel or on one foot, without changing the way the force is coming in, it's impossible to resist much force. I can stand that way (parallel or on one foot), and redirect the push, which makes me very stable, and wears uke out.