Fate- would you suggest holding off feeding him immediately when he wakes in the night?
No, absolutely not IMO. For a long time to come, but certainly while in the newborn phase, a cry is for a need which needs to be met and by far the most usual reason for a cry is hunger.
The awake time I mentioned was through the daytime, sorry for any confusion caused. Even then at 3 weeks baby might not have any awake time that isn't feeding sometimes during the day. At this age babies just eat and sleep, eat and sleep, eat and sleep. During the night, there is no reason not to expect for baby to wake, be fed, so straight back to sleep.
FATE - interesting that you recommend feeding to sleep at this age. Like the OP, this stage with DD1 is a haze, but I definitely ran into trouble feeding her to sleep at the 3-4 month stage, and have been trying to consciously avoid it with this one
Feeding to sleep is unavoidable in the newborn stage (up to 6 to 12 weeks ish). Avoiding feeding to sleep when all baby does is feed and sleep is futile and pointless since when baby isn't feeding, he should be sleeping (not being woken up!).
That doesn't mean feeding to sleep needs to be the be-all-and-end-all. Still lift baby and wind (BF or FF) after a feed at this age. That might wake baby slightly but then put baby down to sleep after the feed. But the almost certainly likelihood at 3 weeks old (and for a few weeks to come) is that baby will go straight to sleep after a feed whatever you do.
By 3 months onwards, that is a different matter. But not something to consider yet.
What you could be doing to ensure better sleep in the longer term is persevering to get baby to accept a dummy and know that sucking it allows them to go to sleep without any help. This takes some 'holding it in their mouth' at this age. But definitely worth the effort in terms of long term sleep and self settling.