Cool!
Last time I played late war, I have made my atacks from a distance of 2-3km, usually during daylight, because it improves theirs but also MY visibility of distant targets.
Spend all renown with falkes. Then, use those fishes to sink the escorts near your pretended atack position.
Now you can approach the convoy again and choose the side with the smaller amount of warships...

When approaching, dive when the convoy is at 20Km from your position.
Do not stay between the side escort and the convoy...
Do not use steam torpedoes.
FaT torpedoes are ineffective unless you know how to use it. Thersīs an excellent manual someone has written about FaTs I forgot where I found it

Target the ships on the opposite side of the convoy. If you are atacking from left, target ships on the right side. DDs will head to the other side of the convoy he he he
Thats it, sorry for my broken english