As a retired MMC (Machinists Mate Chief). I can tell you that posts 2 and 4 are correct. You can be proud of your father’s service, no matter the rate. Fair winds and following seas.
My Dad was a MM3 and my F-i-L was a Electricians Mate 3rd class. Both on Carriers in WWII. My F-i-L said as an EM3, he got to run the projector for the crew entertainment. My Dad said his station was far forward about the third level below the waterline.