Here's a recent thread which I think the 4 hour EASY topic pretty comprehensively
https://babywhispererforums.com/index.php?topic=85278.0I think your nights are a bit more complicated though. I would add that night wakings aren't always a clear 'progression' e.g. babies who may have previously slept through wake at different times because of developmental reasons/ teething/ growth spurts.
Have you noticed any growth spurts? Could one have been going on recently? Sometimes nightwakings continue after a growth spurt for a little while.
Another issue at this age is that a baby can get more distractible and feed less effectively in the day and end up taking more calories at night to compensate. As you say, you can't force a baby to feed for longer but some respond well to feeding in a room with less distraction during the day - even a darkened room. Some babies also take more if they return back to the first breast for a new letdown which keeps their interest (and it will be fattier hindmilk too) OR if you are single-sided feeding then it could be time to move to two sides.
Although at 16 weeks it's not uncommon for a baby to need night feeds if he can go at least 2.5 hours in the day then I would try not to encourage him to feed after 2 hour intervals at night. If he gets into this pattern he may end up taking less in the day and you get into a pattern which is hard to break. It's often thought that if a baby is waking up at a precise time it may not be related to hunger. Even when a baby has woken for another reason they may be sent off to sleep by the breast (as it is so relaxing and contains a sleepy hormone). And it's also so tempting for a tired mummy to offer the breast. Ultimately I think you need to try and focus on getting night intervals to be longer than in the day (again, barring a growth spurt when things might be different for a few days).
Some babies wake for other reasons and then request the breast to help them get back to sleep. Does he drift off to sleep 'independently' at the beginning of the night? I'm guessing as he is on EASY he obviously has got these skills but sometimes I think at night babies seek that comfort (which is perfectly understandable). People feel differently about night feeds - for some people they are not a problem and they actually quite enjoy the chance to connect with their baby so they focus less on getting rid of them. Other people put a higher priority on their own need for sleep as they can function effectively without a certain amount and the need to ensure their baby is not using the breast for comfort every time they wake (which can develop into waking after every sleep cycle and asking for the breast).
I would try your hardest to settle using another method (or even another parent) and see if you can skip the 4am feed at least. If you really have to feed him then give him the minimum you can possibly get away with to try and minimise the calories he takes overnight.
Have you visited the sleep boards too? You could try night wakings. Have a look at the sticky on the gentle removal plan:
https://babywhispererforums.com/index.php?topic=52857.0as that technique might be useful for stopping him falling asleep on the breast if you do feed him at night.
I probably wouldn't advise going to 2.5 hours in the day UNLESS you feel he is showing signs of a growth spurt and your supply could benefit from a temporary boost. How confident do you feel about reading his hungry cues?