fn is the flicker noise, id is the drain current noise, rs is the source resistor thermal noise, etc.
Unfortunately the parameters are not yet documented (there's a request for this), but once you know the basics above it's fairly obvious what they mean (for a couple of more esoteric models it's less obvious, but in general it's clear enough).
Yes, input referred noise is found by dividing by the gain (or gain^2) depending on the units. Essentially the simulator only computes the output noise, but because you told it where the input was, it can also compute the gain from input to output and use that to input-refer the noise.
Regards,
Andrew.