this is something i discovered a while ago, someone here was asking if going "decks awash" was possible and i had a look for them.
my results were the same as yours for "result 2" only the tower above the water. and the AA operatable ( only tested with rear fitting)
i did discover in testing that this lets the enemy spot you at the exact same distance as going in fully surfaced however.
but there is a huge ( was pre patch) benefit to crash diving. it reduces the time immensly ( again not tested since patching)
anyways since patching ive never gotten the sub back into that mode. never could work out how many feet 7 metres was
ill have to give the rest of your settings a try though, if nothing else its a nice effect in calm seas seeing your sub scooting along with only the tower above the water line.