Hello
If I can just throw my opinion out there for you too- see if it helps any
I have a 15 week old (shy of 4 mths) and has recently began to wake at those same hours too. The 4 mth sleep regression is their sleep maturing! They are now cycling between light and deep sleep. It's developmental and just be aware that at this age they make their sleep associations during this phase. So keep that in mind for the long run when working on sleep training
There is also a growth spurt at 4 mths! So I would continue to feed! I BF too and he eats a hefty amount recently since the NWs began a few days ago. I always assume hunger first when BF and try. Lately he also won't resettle after feeds or stay asleep as before, so I try other soothing methods.
Sleep at this stage will bring some short naps which get harder to settle and harder to PD too- again, having to do with their sleep cycles. With naps I would consider keeping appropriate A times in mind and sticking to solid wind downs for both BT and naps. Consistency is key through this crazy change
Many can do 4 hour EASY and as the book says around 4 mths but it could possible be a bit hard to accomplish with the shorter naps too. Naps begin to regulate a bit better and more consistently at around 6+ mths
depending the baby, but usually around there. I don't even expect long naps- it helps
haha!
Personally, I would stick with appropriate A times-- getting him as rested as possible through this change and slowly as time passes you will be ready to work on some ST to help with all that happened during this regression
....I'm there w/ you!
Hugs!