Removing the lower radiator hose will not let all of the antifreeze drain. The pump is above the lowest level of the coolant passages. Also you do not have to remove any core hole plugs (they are not freeze plugs). The drains should be in the sides of the block just above the oil pan. BTW core hole plugs are NOT designed to pop out if the coolant freezes. The are there to plug the holes in the block after removing sand from the casting process.