Derby,

Your unit draws more than 12 amps, so it needs 20amp wiring, fusing.
That's what needs to go to the switchbox from the main panel
.. The heater draws just under 12 amps. So the wiring to and switch for the
heater should be for 20 amps. Neither of the switches that you are looking
at can handle 20 amps. Any hardware store will have 20 amp switches in many
styles and colors.
Your fan draws 1/4 of an amp. It will happily work with the humidity
sensor switch. 12-2 is overkill for the fan but you've already got it so use
it.
So, in sum, use 12-2 throughout, get a 20 amp switch for the heater and
the snazzy FS-100 for the fan. Try to match the 20 amp switch style to the
FS-100. Get your wife's approval on the switch style, color, and
switchplate.

Dave M.