Maybe applying a little oil to the gasket (if it has one) will help.
No, the 3-gallon gray bucket is not food safe. We do not have a 3-gallon food safe bucket. Currently we have only one food safe bucket at Home Depot (search Item# 300197644) which is a 5-gallon white bucket. If a bucket is food safe, it will appear explicitly on a sticker with the label. Leaktite's food safe buckets have a sticker with a spoon, fork, and knife with the words "Food Grade Container - Safe for Use With Food."
I use 5 gallon bucket size red covers on them. I wanted dust protection so I don't know about food storage or liquids. They stack fine.
The outside diameter at top opening is 12 inches. Outside bottom diameter is 10 3/8 inches. The height is 11 inches.