There's dozens of posts dealing with finding those ships. Just search for "AMC", or "Total Germany" or "5 ships" or "Loch Ewe". Remember, patrol zones aren't tied to missions at all. The patrol zones you're sent to are random, they aren't where those ships will be.
There's no TC variable for mission completion, so you can't really set it to drop to 1x TC. There is for Radio Messages, which should be 1x TC and you get those when your patrol is reassigned.
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