Couple of comments. Propane will freeze around -25 below zero. However my 100 LB tanks on my fish house continue to operate at that temp, I am using a 3/8" copper line from tank to heater outside the house.
Propane burns hotter than gasoline, so cutting more holes will not necessarily heat the motor up more.
We have all used a propane gas grill and watched the little tanks ice up. When they ice up, the propane is not going to burn as efficiently. I tell the guys that if its 0 degrees bring the little tank in the house with you. Depending on what you have for a heater, we all have a spare 1 LB tank handy.
With some basic operational experience, you should love your propane auger. They cut like a dream, have almost zero exhaust, no gas or oil to mix, and do not need to be winterized in the spring.
As far as carburetor adjustments, you might be able to do that yourself. The Eskimo auger motors are manufactured and tested during warm weather. They recommend to warm the motor up and adjust the carb, its very easy. They say to turn the idle up till the blade just starts to spin, and then back it off 1/4 of a turn, easy.
The store that has opted to not sell propane augers is missing out. Currently Propane augers are outselling gasoline augers 5-1.
I happen to love my propane auger, and have used it in all weather conditions from 40 degrees to - 35 degrees.