sounds like my dd, i tried smaller feeds more often and she wasnt interested either.
like your ds she doesnt even seem hungry after 6hrs without a feed!
the extra half an ounce of water is fine according to hv and i did it with my last ds as well :)
i aim to get 20oz into dd over 24hr period but some days she has less, some days she has more.
i found myself worrying a lot about this and she is my 5th baby! so i should know what i am doing, tho first three totally bfed and so no clue how much they would take at a feed and ds4 started off not taking much but quickly became a little guzzler with his milk!
i think as long as your ds is happy, content and sleeping well then he is obvviously getting enough :)
and maybe he still associates his feeds with feeling yucky with the reflux, so it may take him a while for that association to go away and then he may enjoy feeding more.
it is a shame, like you i want feeds to be a nice cuddly, relaxed experience for me and baby and we do get some feeds like that, and then we go back to fussing again, i cant see a pattern to it, i have looked to see if there is anything that seems to make her feeds more contented.
the only link i can see is that the days that she fusses are the days that she possets and burps more, but that could be because she is fussing she is taking in more air? or maybe her tummy is making her fuss? anybodies guess, lol!