No deals that I know of on Nikonians that would get you legs of that length for less than $700.
You can use the Markins plates. Arca Swiss originally developed the clamping system that most high-end ballhead manufacturers are now emulating. The clamps and plates have generally retained the original Arca Swiss dimensions, so there is a lot of interchangeability - though not 100% in all cases. We use the term Arca Swiss compatible to describe that particular clamping system and compatible plates. The Markins plates are Arca Swiss compatible.
Yes, the Markins head will bolt right onto the top of the induro legs.