I would feed at 4, 7 and then 10-11 sometime. It is not too late to start the DF.
If you want to feed before the bath and then right before he goes to bed that would be fine. You call that a top up feed. That is what I did with my LO.
If he is waking at exactly 4am I would say that is habitual and not necessarily hunger. Is there something happening in the environment at that time. Like the heating kicks on, the neighbor leaves for work, dogs barking, or something like that that could be making him stir?
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