Can these shelves be used to fire to cone 8?

Yes! These shelves are suitable to cone 8 and beyond. 

The description says it is 'actual 15" diameter'. The image shows the shelf is 16 inches across. Is it now 15 inches across and the image is wrong? I don't know what to trust.

The shelf is 15" by 16" one side is longer than the other.

Hello, Looking for 6 of half shelves 15x7.5"x5/8, for my Cress E23, inside 17.5" opening 17.5" . Do you have them in stock? If not, it seems like you have "18" 5/8" full shelves which says actual diameter 15"" in stock. Is it possible for you to cut them in half for me? If that is possible, how much lead time do you need? Traveling from out of state and i'd like to pick them up to take the shelves with me... Mahalo!

Might be a bit late to this answer thanks for your patience. I would just order the half shelves that are already cut:

18" x 5/8" Half Shelf, actual 15" diameter