My two cents worth on your concrete pillar: I would go 2 ft deep with the 24-inch diameter hole. Try to get as much rebar in the pillar as possible, and I would not isolate the 24-inch diameter section from the 12-inch diameter section. Try to taper the bottom of the 12-inch diameter hole outwards to create an elephant's foot type of effect. Get the highest strength Sakrete they sell, and check to make sure that there are no temperature limitations (e.g. below freezing) on when you can pour it. Use as little water as possible when mixing it to minimize the chance that it will develop cracks. Soupy concrete due to too much water will crack when it cures. If you follow the mixing directions on the bag you should be OK. If you are mixing it by hand it may take a little more water than the instructions say, but go sparingly with additional water. As little as a cupful can make a big difference.
Hopefully, you will never have to remove the pillar.
As for leaving the mount powered up, I do not think that is necessary. As long as you park the mount at the end of your observing session you can power it all down and the mount will remember where it was the next time you start it up. This is true whether you have a permanent or portable setup as long as the mount is polar aligned.
Are you using a Keypad ? If so, you will use the Resume from last position option when you start it back up. If you are only using a computer (with APCC ??) it will be something very similar.
Maybe someone else can comment about whether you should leave the CP4, laptop, and / or keypad out in the observatory. If it were me I would not, especially in the Ohio winters.
Hope this helps