Day/Night feeding confusion!?

[Packergator]

My son is 16wks (18 by due date) and for the past 3-4 weeks has been drinking less and less during the day and more at night. He's now getting the bulk of his calories at night, which isn't ideal if I ever want him to eventually sleep through! Is his tiny mind confused between day/night feeds? I was feeding him every 3 hours but have started listening for hunger cues now (grumbling, etc. which is difficult because he's a fairly non-demanding baby!) and only feed on demand which is working a bit because he was only taking 1-2oz per feed whereas now it's at least 3-4. His feeding pattern looks something like this:
8.00 feed (he's never really interested in this) 2-3oz
12(ish) feed 4oz
4pm feed 5oz
6pm feed 5oz
8pm feed (bedtime) 7-8oz
1am feed 7-8oz
4-5am feed 7-8oz
He definitely cluster feeds in the evening (every couple of hours compared to long stretches in the day) but how do I get him out of the habit of getting most of his milk at night!? I'm afraid of dropping a night feed due to how little he eats in the day. He's otherwise healthy and happy, gaining weight, wet nappies, etc.

Just to add, I have tried giving him more during the day but he obviously doesn't want it; mucks around, chews on the teat, moves mouth away, pulls faces and eventually cries if we persevere too much!

Personally I would start cutting down on the night feeds. I know you say you don't want to because of how little he has in the day, but it becomes a cycle so I think if you cut down at night he will be more interested in the day. He is probably using it has a comfort thing at night, but then it has a knock on effect in the day, and then he starts to need it at night, and so on.