According to this Wikipedia page[0], 81% of every barrel of oil is used for fuel. Although dropping to 1/5th size is not the same as going away, it won't be a very enjoyable ride. The picture might get even worse for petroleum as a chemical precursor once the economies of scale supported by fuel use go away.
Yes and no. Yes there are a lot of uses, but they amount to a small amount of our current oil use. If I read https://www.eia.gov/tools/faqs/faq.php?id=41&t=6 right 75% of crude oil is burned directly as fuel.
edit: note that my numbers are different than the wiki below. I suspect that is because of a difference in what counts for what...
It's the extraction process that's the problem with shale, moreso than the burning of the gas.