Qcmbr
I don't think you can escape the fact that the "twos" and "sevens" (actually 7 x 2) both refer to animals (and actually reflect the mixing of different sources):
And of every living thing, of all flesh, you shall bring two of every kind into the ark, to keep them alive with you; they shall be male and female. Of the birds according to their kinds, and of the animals according to their kinds, of every creeping thing of the ground according to its kind, two of every kind shall come in to you, to keep them alive. Also take with you every kind of food that is eaten, and store it up; and it shall serve as food for you and for them." (6:19ff)
Take with you seven pairs of all clean animals, the male and its mate; and a pair of the animals that are not clean, the male and its mate; and seven pairs of the birds of the air also, male and female, to keep their kind alive on the face of all the earth. (7:2f)
Of clean animals, and of animals that are not clean, and of birds, and of everything that creeps on the ground, two and two, male and female, went into the ark with Noah, as God had commanded Noah. (7:8f)
They went into the ark with Noah, two and two of all flesh in which there was the breath of life. And those that entered, male and female of all flesh, went in as God had commanded him; and the LORD shut him in.
Then Noah built an altar to the LORD, and took of every clean animal and of every clean bird, and offered burnt offerings on the altar.
We are talking about a story. What happens in the story is what the story tells, nothing else. Adding foreign elements (such as, local flood, breeding in the ark, animal food for animals and/or humans) can only make us lose the story. In the story economy more than a pair of clean animals (and the story doesn't mind about the anachronism) is necessary for the final sacrifice episode. That's about all I guess.