You will likely find that 6 scoops per bottle just means it's a smaller scoop than the formula you are using at the moment. Afraid I can't really comment on the formulas you mention as I have not used them, but I don't think giving him extra at night will cause constipation. You could always try giving him more at his last feed, or try giving him a dream feed before you go to bed yourselves - that's what we did with Sam right up until the point where he was one solids and didn't seem to need it any more.

BW