I am no expert but if possible I would try having your husband/boyfriend/friend try feeding him his bottles at first. Perhaps even choose a time of day that he always gets a bottle to start off and get him used to taking the bottle regularly. Then introduce it more and more, weening him from the breast. Often babies refuse the bottle from mom when they know they can nurse.
As far as how much he should be taking... it's a bit individual. For my son (8mo) who takes formula and also has solids 3 times per day, he typically eats 4-5oz at a feeding. Our pediatrician told us to try to get to 24oz of formula each day but we usually are between 20-24 for the day.
HTH!