I take it I should leave my Ace B-17 crews sitting in their burning aircraft until they can be swapped into new B-17Gs or can I swap them into fresh B-17Fs?
Unlike all other aircraft types, you should have a decent number of veteran daytime bomber crews. Any B17 that is "damaged" (i.e. destroyed and replaced by the damaged aircraft) automatically gains veteran status. I typically put them in B24s, once I had those available, to take advantage of veteran status on the more powerful bombs. Of course, this depends on the ability of damaged planes to survive return trip. You're probably still a little far away from B24s, so I'd advise putting your crews into fresh B17s (they'll have to be full health and full movement to make the switch), and putting the veteran bombers in the centre of the formation, in order to use their more effective veteran bombs.
My advice for trying to get a few hurricanes to vet status is also partly because the fighter bombers can't get to high altitude, where most planes usually stay, so they have a hard time becoming veteran.
There are no destroyer flotilla or other sub-hunting surface fleets I take it?
That's right. In the first iteration of the game I tested, I spent large parts of my turn blindly moving around destroyers hoping to run into a submarine. Once you manage to clear the Atlantic, searching for submarines becomes extremely annoying. They
could be there, and it costs nothing to search, so you
should search, but deep down you know the German player has probably given up contesting convoy passage. With this system, a stray sub is unlikely to sink your convoy outright, so you can send it across, and simply counterattack with Sunderlands once the wolf pack reveals its location. Of course, in the early part of the game, you'll find it useful to take a more active role in anti submarine activities.