It is pretty normal for them to be sleepy for feeds still. Mine both woke up a lot at 3-4 weeks old. Sometimes a diaper change in the middle of a feed helps. Or talking to them, rubbing their back, massaging their legs while they nurse will keep them more awake. Each baby is a little different.
Awake time will probably be 30-60 min at this point, starting at when he wakes to feed. So if he nurses 30 min, he may only be happy/alert for 5-20 min before it is time to lay him back down for a nap. Very calm alert periods, like staring at you or a wall, are the best active/alert periods at this age.