u'll be seeing temps of -47*C, that is the boiling point of R404.
the vapor pressure of r404 is 182.1psi, so your good there.
looks like your not getting taken for the perverbial ride as they say.
Ref: Dept of Defense Haz Mat Info for Cornell U
as for exactly how much heat you'll be removing (how cool your chip will be) i'd need to know the mass flow of r404, surface area of your chip, and the amount of heat the chip radiates... i'd also need to figure out the specific heat capacity for r404...