Concrete base problem in garage shop. Any construction folks?

Thanks for all the suggestions. The new floor will have #4 rebar in a 2ft grid pattern. I said unstable because my Kubota wants to spin in the crushed base. Like suggested, when I compact it, put the vapor barrier on top with the rebar, it will be fine. I usually overthink this stuff since I’ve been a technician my entire life. The floor failed due to a broken and settling footing on one side. It caused upheaval and cracked. That’s been fixed with post and beam installation. The building is stable now and I installed an under footer drain on the low side. I noticed the water draining during the heavy rain today. We have all clay and it tends to hold water if it doesn’t have anywhere to runoff. The floor will actually be floating slab and not anchored to the footer. It was originally a monolithic slab deep pour. I've always used 3/4 or #57 when I poured sidewalks and pads. That's kind of why I was leaning that way. I'm thinking I should just put more 3/8 on it and be done with it. I don't know any concrete folks. Keep suggestions coming. Craig