According to King Arthur, one of its 5-lb. bags of flour contains about seventy six 1/4-cup servings. That's about 19 cups. A 50-lb. bag would therefore contain about 190 cups of flour. At four cups per quart, that comes to 47.5 quarts. So, the container you have in mind is not big enough to hold 50 lbs of flour, even if you compact it by jumping up and down on it. It's what in my youth was referred to as a "blivet" situation.
As far as freezing the flour outside, I suppose that cold is cold, but if you are talking about freezing a 50 lb. bag of flour, Tom Lehmann recommends that one freeze a 50 lb. bag of flour (in a freezer) for 45 days to rid the flour of any bugs. However, if you use a lot of small buckets, you might be able to rid the flour of bugs if the weather remains cold enough long enough. When I freeze flour in my refrigerator freezer compartment, I do it in 5-lb. quantities for about 3-4 days. I just guessed at that number.
The RMC1286 Rubbermaid food storage container you referenced should work for your purposes. However, one of the most popular brands of dough storage boxes among pizza operators is the Cambro brand. The Cambro unit is made of a polycarbonate material and apparently can tolerate a fair amount of abuse, which is not likely to be a factor in your home kitchen. However, the lid for the Cambro unit is priced separately, and it is quite expensive. The Cambro dough box itself is priced around the same as the RMC1286, although when I researched the RMC1286, I could not tell whether the lid came with the unit or was priced separately. So, whichever way you go, be sure that you price in a lid if it does not come with the unit itself.
American Metalcraft is another well known supplier of dough storage boxes. You might also spot a good deal on eBay.