When Lieutenant Paris has finished lighting the candles in their quarters and sets the lighter down on the center piece the camera cuts away to his face. When it comes back to facing his back with Lieutenant Torres in frame the lighter is gone. Since he had just set it down it's not possible to have moved that quickly.
B'elanna Torres has said, in season 5's "Extreme Risk", "When I was 6 my father walked out on me...." The flashback here shows her to be 12 when her father walked out on her.
Tom Paris asks Tuvok for advice on fatherhood, saying he doesn't know anyone else who's been through it; however, he knows Joe Carey and knows that Carey has daughters, and might know that Ayala has sons.
The doctor says that Klingon gestation is thirty weeks but that a hybrid (Klingon/Human) is likely shorter. Given that human gestation is forty weeks, surely the anticipated hybrid gestation would be longer.