Shinawill
DHL Air UK Ltd. is an EMA based airline wholly owned by DHL Intl. operating a fleet of 22 757 freighters.
HdH
Your question has been answered on a different site.
Wheelbarrow
Eating a sandwich now and then out of a vending machine will not cause you to flunk a medical. Eating solely out of a vending machine might. I trust you can see the difference.
Baps
There is plenty of time to sort out your catering prior to departure, and as you so rightly point out DHL turnaround times are quite a bit longer than pax operations normally are. So there'll be plenty of time to stock up on the catering at transit stops. That is, if you take the time to buy something to eat, rather than gossiping and subsequently posting unfounded rumours on this here board.