3 mice in a single feeding should be plenty if you are feeding him once a week. BPs are opportunistic feeders. They will eat till they ar efull if given the chance. He was probably still in feeding mode when he was striking at the glass. Just feed him and then leave him be for a day or two. Also, it may help to handle or interact with the snake between feeding days so he doesn't associate any interaction as just feeding. Otherwise he is just likely to go into feeding mode whenever you approach.