1. Given that it takes about two weeks there and two week back I find a mission lasting one month quite short. Did you patrol at all, or just drove there and back? When you begin the mission they give you an objective, and once you complete it you are supposed to radio in to get another one. They'll keep giving you new objectives until you have less than 7 torpedeos or your fuel level is under 10%. Given that it takes about 25-30% of fuel to get back, I'd stop radioing in after the fuel level hits 40-50%.
2. I can't say if your mission was a failure or not because you didn't include the objective there.
3. It was most likely somewhere outside Honshu, and iirc I sunk abou 20,000 tons worh of shipping.
4. You have to install the radar before you can use it, and it doesn't become available until about mid-42.
edit: Woot! Too slow
