Hi and welcome to BW!
I wouldn't jump to a 4h EASY straight away and I also wouldn't look at the cycle as a 4h cycle, but rather the right A time for him + a good nap, which will equal his EASY cycle. I don't have the book with me right now but I would suggest you start with the routine you have now, i.e. 3h and increase A times gradually. You can do that by increasing 10-15min A time every 3-4 days till you get good naps, baby is not OT and the cycle is approx. 4h (some babies do a bit less, some babies do a bit more). Increasing his A times will push his naps as well and therefore the feeding and hopefully he will feed more.
Saying that, I wouldn't expect him yet to STTN even if he used to do it. Babies change and grow and their night needs change as well. If he STTN then great, but I wouldn't "pressure" him to do so at this age.
3NF is what we also had at that age and my DS was FF by then. EBF babies take much longer till they can go long stretches at night without a feed.
For now I would keep NF as they are and wouldn't try to wean any of them.