hehe, Im flattered to be asked so many questions, really.
an almost perfectly controlled hamon(one that follows your clay) can be gotten at 1500F, I austenize at 1400F (for safety from failures, and for hardening depth)with a couple mins of soak, and get a good active hamon.
So I would say shoot for below non magnetic 1500 by a small amount, maybe 1450F, and soak it there for about 2 mins. The soak will cause it to austenize(become non-magnetic), once it does this soak for at least another minute.
This can be tricky over the fire. I used to do it this way, its just an aquired skill, give it some tries and youll get it soon enough.
To me hamon(edge-pattern) is the term for a well controlled differential. Clay is the only way to do it, I know of. Everything else is a temperline, to me. you can get a temper line quite easily, and theres lots of techniques used to do it.
Joe