Level an existing pad for tool shed

Hi, I have an existing 7.5' x 14'x 4"thk concrete pad that valleys in the middle and drains to one side. I want to level it and build a tool shed on top the full size of the slab. Location is in Georgia. Can anyone suggest:
1. what should be the minimum thickness for the topping slab.
2. is rebar or wire mesh necessary?
3. what options do I have for anchoring since there will not be enough embed depth for j-bolts?

Thanks