My garage has two inches of foam over the Polyethelene Sheet. Under the poly I have sand so it was fine. Since you are using stone placing the foam under the poly will protect it from stone punctures.
I do think however that the rebar is overkill for a garage slab. I would use the fibers...
I have the old rotary phone from my old house. It was free and it is indestructable. It is a bit a a pain to dial with in this age of long phone numbers.