And obviously, ONLY MEN can sacrifice for their loved ones...
Piffle on that argument, I say.
It seems pretty obvious that this movie does not start on Earth-199999, just from the visuals. The FF's world doesn't match the MCU-Earth esthetic.
Where it ends, goodness only knows.
If that climax is against Galactus... not likely. In the comics, when Ben and Johnny tried to fight Galactus, they just... bounced off. As was appropriate.
We all know how the FF beats Galactus the first time out - The Watcher sends Johnny Storm to get the Ultimate Nullifier from Galactus' worldship. Threatened with it, the Big G agrees to go away.
You can have a big fight at the initial meeting with the Surfer, ending in the usual team-up when heroes fight. You can have a big fight against G's "Punisher" cyborg....
And you can have a big fight when Dr. Doom tries to grab the Nullifier, which ends in a malfunction that transports them all to the MCU... or however we justify a Doom that has Stark's face...