The 32" ID is measured from the inside bottom of the pan. The OD, or Outside Diameter, is measured from the top outside lip of the pan ( the largest width) and is 34". Your space will need to be able to accommodate that 34" Outside Diameter. We recommend that the Inside Diameter (ID) of the pan be at least 4 inches larger than the diameter of your water heater so that it will have a 2 inch clearance all around when sitting inside of the pan.
The thickness of this item is .095.
Yes, this will be compatible with a 50 gal. water tank.