So glad your Dane made it through the surgery ok, poor baby!
I make sure to keep my dane's food and water elevated, don't let her gulp TONS of water after eating dry food, and don't allow her to run or exercise vigorously after eating. They say that these thing will help prevent bloat. Still, I watch her very closely after she eats.
If it can't happen again after stapling, I'm certainly glad that you two are in the clear!
I don't mean to offend, but would you consider feeding him a higher quality food? I know that the advertisements are very misleading- so it is difficult for a consumer to know any better, but the foods you mentioned are not very nutritionally sound. There are many threads on here about the quality of different dog food, and I'm sure you'll find a lot of valuable advice regarding brands. Just do a search for "dog food", and you'll find many to browse through. I got quite an education here myself when I first signed up, and found that I was not necessarily giving my dogs the nutrition they needed. So again, this isn't a criticism, just a friendly suggestion.
I would LOVE to see pictures of your baby!