Re: irimi nage spinning
This is interesting. At our dojo, we don't pivot after irimi. We snug uke's head to our shoulder and drop our forward foot back at 90 degrees. Then we step straight through with the same foot. When it's done well, it's like dropping into a deep, dark hole.
The 180 turn is amazing, but I can never seem to carry it off. Uke often ends up spinning out. Indeed, when I take ukemi from someone executing iriminage with a 180, I often feel that I get my balance back and can reverse. I imagine that's often an illusory feeling.