50 acres of crop land won't support the 200 folks you say this facility will house. if you grew corn and got what Dept of Ag says of 70 bushels per acre at 56 lbs of shelled corn per bushel you'd need at least 56 acres of crop land alone and that would not allow for crop rotation.
And that doesn't take into consideration raising cattle hogs sheep or fowl for meat.
Also even if you use jail cell dimensions 6'x8' you'll need right at 10,000 square feet to just house them.
Also a half million gallons of water only last 200 folks about 25 days at 10 gallons per person and that's a very low amount and will take a storage container 100' X 100' x 6.5' tall or so.
Lastly it things go really hooptie you're probably going to need draft animals - mules, horses, oxen - to replace such items as tractors tillers and other forms of transportation. My guess would be at least 50 horses just to get by and then you'd need a source of feed - oats hay etc - for them
I would be supprised if you could get by with anything less than two sections and more likely five to be on the safe side