Learn English – Meaning of “up” and “off” in “I live up north off some_region”

Either is appropriate, and in my opinion equally so, depending on whether you are trying to emphasis the blockage of the obstacles or the length of the road along which they appear.

Look past means look at a point beyond. You might

Look past the building at the shop down the street or, figuratively,
Look past his opinions to his actions.

I don't know on what authority your article suggests that look by is a synonymous with look past. I have never encountered that idiom. The only sense I can immediately make of look by is look at a point next to:

Look by the building for an alley running north.
*Look by the computer and you'll find a notebook.

By here is simply a preposition, heading a prepositional phrase of direction. Look past is probably to be parsed similarly, but it "feels" a bit more like a phrasal verb, perhaps because it is used figuratively as well as literally.