It is weird! Does he get a nightly bath? Maybe he's peeing when he's in the tub?
If it weren't for the low pee diaper output, I'd be pretty much completely unconcerned because everything else looks completely normal. But given that diaper output is low, what would you say to seeing a lactation consultant, preferably an IBCLC? See if she can tease out what's going on with supply and help you get a sense of how much your baby takes at the breast?