What you can do is use distraction or whatever you can to delay his bottle to get him to 3 hours. You may need to stretch him slowly at first, but if you can get a 3 hour gap between his first and second bottle that should mean he takes more and can then last longer until his third bottle. If he was going 3 hours between feeds when you were breastfeeding then he should be going at least 3 hours on formula.
You may find that the next size teat is better for him, he had to work harder at the breast to get his milk so he may well need a faster flow teat on a bottle, or a variflow teat he can control himself if your bottle type does them. It's worth a try!
Laura