I replied in your other post but given what you've said here the fact he's taking 3.5oz is quite good. I don't think I'd offer the breast after the bottle if I were you. He may not actually be that hungry but happy to suckle since it's comforting. Not sure but that's what I would try. If he's really hungry, I'm sure he'll let you know.
As for how much in the bottle for 5 feeds. Again, it's going to vary from child to child but I would try for 5, 5-6oz bottles.