Of course the WHO says this, because the WHO is the 'World' Health Organization, and it has to account for the lowest common denominator- a country with no sanitation, rampant disease, bad water, no way to refrigerate, no education, and the like. In that case, homemade formula would definitely be dangerous.
Of course nobody wants to have to make their own formula. I would do anything to be able to nurse my baby. Anything. But after weeks of having to literally dig rocks out of my DD's bottom [sorry, TMI] and begging dozens of random women for their breastmilk only to be declined because my child wasn't local or "sick" enough per se, I needed to find another solution. Only when you have experienced this desperation will you understand why I and others take this risk. I would like to hear a testimonial from a mama who has used the WAP homemade formula and it caused harm. (By the way, I don't agree with a lot of the other WAP and raw milk stuff, so I'm not a blind 'follower.')
Also, most donor moms do not want their milk to be pasteurized and they will tell you so-they feel that much of the benefit is lost through pasteurization.
Back on topic: To the OP! The baby does seem to be drinking too much, maybe in an attempt to comfort nurse. My 6mo DD drinks 6oz 5 times a day and even that seems to be too much. I would see what happens if you have the baby take 1-2 oz every hour or so, more like a boob baby does. I don't know if you can reverse the overfeeding habit, but in the meantime maybe try the Breastflow bottles someone mentioned, various pumping strategies on Kellymom, and try some galactogogues. Hopefully the supplementation argument is a moot point for you!
:
