1. How can the US economy be awash in rising oil prices?

When he wrote about an item in a parenthetical, it is the same information of time or currency. It is there to add extra information about the time and not about prices. This should be moved closer to what it describes.

1. The tower will replace the existing Tokyo Tower in 2020.

Apart from the illogicality of something that has already come into existence replacing something else only in the future, I would say that since the location of the tower is not the most important point of the sentence, em dashes are the stronger parenthetical mark