just a few quick things:
if he is still rooting after a feed, offer breast again. your bosdy is constantly producing milk, your breasts are never empty, so as long as he is sucking he is getting milk
babies will nearly ALWAYS take a bottle. even after a really, really good big feed. they just do, it is no indication of how hungry he is, or how much milk you have.
expressing is also no indication of your milk supply. ds could be getting loads, and how much you can express afterwards doesn't mean that much, iyswim??
i think, that if you want to exc BF then this is what I would do:
ditch the bottles and demand feed.
you shouldn't need to top up- just keep offering breast if he asks for food
if you do feel that you need to keep giving the formula for a while then you could just gradually reduce the amount you are giving at each feed.
so, if it's 2oz then drop to 1.5, then in a few days drop to 1, and so on.
it is hard sometimes, but you need to regain confidence in yourself and the fact that you can and are producing food for your baby. the more you feed him the more you will make. the more formula you are giving the less he is stimulating yourt supply. it's a vicious circle really.
well done for getting this far though, I had a breast refuser first time round (interesting also only latched on at 10 days old) and it's soul destroying. but you';ve done well, and if you want to exc breastfeed then you can!
have you spoken to a BFC at all?