We had the same thing with H. I stretched the feedings to 4 hours during the day over about a week. I distracted him by playing with him or using the paci. He still sometimes wants to eat at 3.5 hours but he definitely goes longer at night now. Other things that helped us get longer sleep: swaddle, putting the paci in when he thought he was hungry, and WHITE NOISE. Seriously. When we started using white noise (continuous, not the sleep sheep!) he extended his sleep by up to two hours. It was huge for us.
You could also try cluster feeding. Feed him the 4oz at say 7, and then another 2oz at 8 before putting him to bed. It didn't work for us, but I've heard several people say it worked for them. GL.