Thank you, everyone, for your incredible advice and generous responses to my post!!! I'm really floored by your generosity and, as always, appreciate the wide range of opinions on BYC, even if they are wildly different
Young Mr. Bieber has not had another bout of aggression. This is not to say that he won't and I'm very vigilant when I go down to the coop. We recently enclosed the run to make a huge aviary area for the chickens and I've been spending the weekends cleaning out the coop and moving things around. I think he might have been stressed by all the commotion the day he pecked or scratched my legs.
We won't be breeding him since he's not very attractive (sorry Justin Bieber fans, but the other roosters we've had were stunningly gorgeous!) and our hens rarely lay eggs. The vet confirmed that we have Marek's (by sending out a pathology sample from our beloved grey bantam), which she said might explain why we rarely get eggs, especially whenever there's variation in the weather. We've tried all kinds of feed, treats, nesting boxes, etc. No new birds will be joining our flock for a very long time and we wouldn't raise any chicks right now given our Marek's situation. If Mr. Bieber shows any more aggression or if the neighbors ever complain about his crowing, we'll have to cull him since I wouldn't feel comfortable rehoming a Marek's exposed bird.