Good suggestions, the moving water would help if there were electric available, but then I could use stock tank heaters. I was impressed by how far you thought through the additives and the freezing levels, etc.
Solar is also a good thing, except I am on a limited budget and can't afford to buy or make it.
Hopefully I will be able to afford to move my horses to a barn that has a manager that thinks ahead and prepares her facility for such occasions. Meanwhile, I am off to drive a half and hour to break ice, and add water by gallon containers so my horses don't colic!