Glad you asked about the spacing. I'll get an extra picture of that.
About Tesla's tuning, here is a quote from his pre-hearing interview 1916:
In these demonstrations, which I showed these effects, these most powerful effects that were the sight of New York at that time, I operated with frequencies from 30,000 to 80,000. At that time I could pick up a wire, coil it up, and tell what the vibration would be, without any test, because I was experimenting day and night.