6 oz a week is very good weight gain. what was his birht weight?
it is normal for their weight gain to tail off around this time.
you say it is reflux but I am not so sure myself about this diagnosis.
it is normal for babies to wake alot - i know that is not comforting to hear - it is just that it is not what we are used to adn what society expects from babies.
i don't think weight gain will be better on formula. ff babies may sleep 'better' because so much of their blook is diverted to their GI tract for so long to cope with trying to digest something that is harder for them to digest than bm.
have you ever gone to a breastfeeding support group? one that is run by the NCT, LLL, BabyCafe, etc are very good for answering the questions you have and seeing mums with babies older and younger than yours will help you understand better what is normal for a breastfed baby. many times, if your family is only used to seeing ff babies, their expectations can be 'all wrong' for a bf one and without deliberately undermining what you are trying to achieve, it does happen.
about the exhaustion, are you feeding while lying down -day and night time helps a lot with the exhaustion.