I use a electric oil filled heater in my RV. I leave the thermostat on low and it works fine. We don't have many real cold spells but it hasn't been a problem keeping it above freezing.
Try to find a ranch type fence builder. Ask them to do it in between jobs or on a Saturday. If you were 20 miles east of San Antonio I would do it for half that. You might also look into renting a skid steer with an auger.
I like 1/4 drive. I use it a lot on motorcycles. I'm much more likely to over tighten than under tighten. I like to use the smallest drive size that will work.
I have the m18 grease gun. It has worked very good for me on heavy trucks and equipment, farm machinery. It is very powerful and seems like it's holding up well
I have had good luck with the milwaulkee 1/2 drive m18 fuel brushless. I have not found anything it will not break loose or break the bolt. I went over 20 years with no impact at all but thanks to garage journal I found out about how much everyone liked the milwaulkee and got one over a year...