Let's look at your sentences and explore their meaning.
食べ物が美味しさですか
This says, "Is the food tastiness?" I don't think that's what you want to say.
食べ物が美味しいんですか
This could possibly work, but it still sounds a bit off to me. (But, I'm not a native speaker.) What strikes me odd here is the use of the particle が. Had you written it as
食べ物は美味しいんですか
to my non-native ear, that sounds better.
美味しい食べ物ですか
This just says, "Is it tasty food?" This sounds perfectly fine; perhaps this works for you. But, is it really saying what you want? For example,
日本料理はおいしい食べ物ですか
"Is Japanese cuisine tasty food?" That could make sense.
食べ物の美味しさがありますか
This sounds kind of weird, "Do you have the tastiness of food?"
This one you could probably change a bit, to
食べ物は美味しさがありますか
"Does this food have any taste to it?" Perhaps you think the food is too bland.
Probably what you want to ask is just
食べ物はおいしいですか
"Is the food tasty?"