As promised, this is my latest update on this project. After reading through the forums here and discussing with several local friends I decided getting an inexpensive generator was the best overall solution.
So I went to Harbor Freight and bought this with a 100 foot 12/3 drop cord:
I tried it out in my backyard and it seems to start, run, and work perfectly. So far, so good.
Still considering my other longer term options, including changing the CO/LP combo detector out for an LP Only model AND, at the same time, swapping my Smoke Only detector on the ceiling for a Smoke/CO Detector. More on those later ...
Thank you all for your help & advice.