Re: WHat is food grade beeswax
All real beeswax is "food grade" unless it has had foreign substances mixed in. Consider that "comb honey" is a combination of beeswax and honey, and is certainly "food grade".
Having said that, wax from rendered brood comb, which may contain some amount of miticides/pesticides if you treat your bees would not be my choice for "food grade". Also note that you really don't know what is in foundation wax, unless that wax is exclusively from your own hives.
USDA Zone 7A Elevation 1400 ft