Saacsmum - my friend's DD was also way down in the plunket weight charts. The plunket nurse made her feel like a totally incompetent mother as she was continued to go down on the chart and was eventually below the recommended weight for her age. Her paed told her not to worry, as the charts are AVERAGE weight, and as Moari and Islander babies tend to weigh a lot more than non-Moari and non-Islander babies the AVERAGE weight on the charts is much higher than they would be in other countries.
However, the paed told her that as long as DD was developing well, was alert and meeting other milestones, then there was no need to worry. Some kids are just lighter than others. Her DD is now 2.2yo and is still a skinny child - but perfectly healthy.
It turns out that the child is one of those with a fast metabolism (she was very active even before she could walk, she was always bouncing around), and she's never has sugary foods/sweats.
The plunket nurse had made such a big deal of it that my friend became a nervous wreck about the food issue for about a year and a half. Because she was so focussed on this food issue, she really lost out on a lot of the early enjoyment that she could have had with her child. Also, because it became a stress issue for the mum, the child did pick up on it (even though the mum tried to be lighthearted about it) - and this may well have caused some eating difficulties where there might not otherwise have been.
You don't say whether your child has started crawling. Remember, once they start moving around, they do often loose weight.
To me, the volume of food your little one is eating sounds pretty huge (yes I realise that this is on a good day). I was once told by a doctor that because babies have such variable apetites, you need to look at their weekly consumption (not daily consumption) and average it out that way.
Personally I did not find that general day time feeding had any impact on my DS wanting to feed at night. However, what did really cut down on the night time feeds was something to eat just before bedtime. We got into a routine of yoghurt just before bed (but you could feed other things as well, eg cereal, stewed fruit etc. A friend of mine always gave hers custard). We did this as close to bedtime as possible (just before cleaning teeth). We didn't force the issue, and only gave it when he wanted it, but were surprised to find that on most nights he did want his pre-bed food (it was not a large helping, though)
If you are concerned, see a paed and do not be bullied by plunket. My friend really wished that she had sought a paed's advice sooner, because it would have saved her a lot of stress and worry.