Really as quick as I usually am to jump in on Enterprise's flaws, I gotta give them a pass on this one. All of Trek is guilty of this one. Gastric translator? Why not?
As for the breeding, medical technobabble at it's best. Phlox was able to do some magic to let T'Pol and Trip breed. Bashir the same with Jadzia and Worf. Unless we want to think one of them invented a "embryonic translator" or something.