torpedo bombers cannot act as their own AA suppression aircraft.
They need other aircraft, even of the same type but without torpedos, to do the AA suppression mission just before the torpedo planes reach the drop location.
It is simply geometry. If the torpedo bomber with a 40kt torpedo is attacking a 20kt ship and drops from 1200 yds away, it has to be pointing at a spot in the ocean 600 yds in front of the target ship. Fixed guns have no hope of hitting the target ship before the torpedo is dropped. The torpedo plane (at least early war) has to fly a steady course so the gyros in the torpedo can stabilize.
No wild jinking or maneuvering, the plane has to be flying level and at the right altitude or the torpedo will not enter the water correctly, It could dive to deep, skip on th eserface, and/or even break into pieces.
Adjust torpedo speed, ship speed and drop distance as you see fit but unless the ship is very slow or dead in the water the torpedo bomber needs to lead the ship (point ahead of it).
A well armed plane or planes could certainly circle back and strafe a ship or ships in support of a 2nd wave of torpedo bombers.