It's impossible to propagate a species from only a single mating pair
The task of acquiring two of every land animal on the entire planet and fitting them on a single ark is a task akin to Santa Clause going to every Christian child's house in one night and storing all of those toys in a single bag
It was clearly an embellished story of a major but localised flood and Noah probably saved like, a farm
I feel your third point is most accurate. I think a huge flood may have occurred and perhaps some dude named "noah" toughed it out. But legends end up growing far beyond themselves.