What is the formula for heat of vaporization under reduced pressure? I haven't taken a chemistry class in several years, and I have honestly been searching the web for the past hour and can't find anything. I know this is something basic we learned back in high school chemistry but maybe I am not searching for the right term...

Is there a formula? I know how to calculate distillation speed based on wattage, and the vaporization constant of the molecule, but cannot find any particular formula that can calculate how that number changes under reduced pressure.
You are looking for the Clausius-Clapeyron equation.  It comes in various forms:

The exact version is

$$\frac{\mathrm dp}{\mathrm dT}=\frac{\Delta H}{\Delta V T}$$

or, since the volume of the gas phase is so much larger than the volume of the condensed phase

$$\frac{\mathrm dp}{\mathrm dT}=\frac{p \Delta H}{R T^2}$$

or even more succinctly, assuming $\Delta H$ remains constant

$$\frac{\mathrm d \ln p}{\mathrm d \frac{1}{T}}=-\frac{\Delta H}{R}$$