Okay, I tried 'Happy Times' with my setup again, this time running Game Booster, and it got all the way to the 'Not so long ago..." screen, then it crashed.
I made an entirely new game, put in nothing but the MFM, and it loaded 'Happy Times' just fine.
I started a test career with my full setup, set out for AN44, waited out days of stormy weather, and finally encountered a ship. Wow! M17!
He was marked neutral, but he was close to the English coast and heading in that direction, and when he saw me he started zig-zagging like crazy. Who cares if all five torpedoes missed or were duds? The MFM runs! I'm worried about meeting a bunch of them in a convoy, but then I don't think that should matter. I don't know why it won't load 'Happy Times', but I'm not too worried. It's my favorite Single Mission, but then I only use it for practice or to relax, and I'm not really that much into single missions.
It runs MFM ships in campaign. That's all that matters. I'll be starting a real career soon.