Should we count the things you did wrong...
If you had 12 men killed, sounds like you left men on the DG, AA guns, ect.
You can't leave them there dived as the game still sees them on those stations and a charge will kill them. Place them in the alley or damage crew, but never load your sub with so many men you can't move them from the topside gun stations. If not on the DG, you were just too shallow and they scored a direct hit.
Early war you probably didn't have surface radar and your men have poorer skills. If you have a contact, don't use TC until you have everything figured out. They can hit you with a dozen shells before you get slowed down. Often you can see them, but your men can't.
Instead of fighting escorts at scope depth, I would've dived deep and evaded and saved my torps for the TF if a end around was possible. I'm sure they slowed when you were spotted. Very dangerous fighting multiple escorts, you set up on one the other blast you with a good run.
You didn't get phantom damage. No doubt while using some TC a escort made a run. Even 8% TC under battle you can die and the escort be long gone before you slow down. So with TC you got attacked and the DD had made his pass before you slowed down. It's also possible a plane made an attack on you, happens all the time.
Not sure how many skippers you had, I would think RFB limits officers and you would be very limited anyway at the start of the war.
That was a Kongo.......