A Catalina could take a torpedo or two 1000lb bombs under each wing (or side of the wing rather). The more usual load (shown in the pic) was 2 500lb and two 1000lb bombs. Several Black Cats (like the one pictured) were also equipped with 4 .50cals in the nose for shooting up barges.
Detering was as effective as sinking. But U-boat sinkings are very hard to verify. I'm not sure an accurate account of how many U-boats a particular ship or plane sank could be determined.
Exactly. A U-boat had no chance of keeping pace with a convoy when it was submerged. If the Sunderland, Wimpy, Beau, Avenger, Hudson, or whatever else was covering the convoy could get the U-boat to dive, the convoy was saved (at least from that U-boat).
Yeah. The Wolfpacks were terribly effective. But it's not like the convoys were only capable of attacking/detering one U-boat at a time so that helped.