Been in this situation, just the other side of the strait...
a) NO not in a type II, same convoy same escorts, the weather can only clear up and either the escorts or a plane will spot you, you can't outrun them, not even an armed trawler, or dive properly to evade, ergo you're dead
b) Possibly, it's what I did, if you get lucky and the visibilty is real bad you might evade the escorts on the surface, but if they spot you, you're dead, like me
c) Doable, 1000 tons or so per DD, you might take out 2 or 3 that's decent tonnage in a type II, but be sure to kill your target or it will kill you.
All in all, not a good situation, radioing in the convoy won't help either in 1939, no friendlies close enough to help out.
If you do want to go for option A) try to be at least 3km out and submerged when the weather clears so you can go for long-range shots, that might work.
My choice would be to radio them in to BDU, consider your job done and wait for a lone fat merchant to take to the cleaners, in that area you won't have long to wait
