How much is the large size?

It’s best to refer to the size chart. The only way to know for sure which size is best for you is to measure and refer to the size chart. Not all “large” sizes are created equal.

What size clothing would a person who is 5 feet 3 inches tall and weighs 115 pounds wear?

Small size

I am 5’1″ and 140 lbs. What size will fit me? Medium or Large?

I would try a medium. The fabric is very stretchy and the large will be too long for you.

Are these thin or warm?

It is a medium weight velvet fabric that is not thin and not heavy. I would not wear it when the temps are over 70 degrees. I would wear leggings underneath when the temps are below 50 degrees.