Well the breeder was becks bird Barn & i have heard some bad reports about them ! a small cage is ok for the purpose of just a sleep cage,but ideally greys should be provided with a large cage.Jealously may well be his issue & may be linked to the plucking,he may pluck to get your attention,i personally would refrain from sitting next to him with the other pets.Never react to the plucking as this will only reinforce the behaviour, give him plenty of baths/sprays with the addition of some aloe vera juice.