TBH, at 3.5 months I would just quickly feed and get him back to sleep when he wakes at 2.30. At that point it's been 4 hours since his last feed, and if you feed at 2.30 he may go back to sleep til morning! If the paci was settling him for a good while, I would say it was a habitual waking but because he wakes up again very soon after it does sound like hunger.