Yes, it's good paint for the price.
Yes, can be as primer as long it's not semi-gloss.
no primer in the paint
you would need to us brand called Kiltz for those spots
I would not recommend it it's very poor coverage and is not meant to be adhesive to galvanized I would go with a metal primer instead of your choice then top coat it with a exterior grade paint
I find that this paint as well as any other ceiling paint will require at least two costs. If the ceiling is darker and you may even need three costs. Make sure you let the product dry in between coats...
Not 100% sure, but most ceiling paints can be tinted a few shades darker, I would check with the that department to see if it can be tinted darker colors....
53 to 54 pounds for the 5 gallon bucket...
Berh is ultra white, while this is more light grey
I would recommend primer, product does not have cover efficiency for bare would.