I agree, too much oatmeal would be no good...I already use it to win my way into Winston's heart, too. It is by far his favorite thing in existance. When I first got him, he was terrified of people. Now he comes running to be petted, and ejoys licking a few oatmeal flakes off my hand.
I actually decided to just stick with the petting and no food, because Frank gets excited and this encourages Winston's temper even more. Luckily, Frank was born with infinite patience and just sits there and lets Winston sniff her when I scratch both of their heads.
I also realized that at one point, when they were still bonded, Franklin would actually go over to Winston and stick her mouth into his, and steal his treat!! I always gave him a replacement treat and he never seemed bitter about it, but I wonder if this might have been part of the cause of their fighting. I would be mad too, if I were Winston. Maybe his patience just gave out.
anyway, I'm just going to give him a few months before I get into more serious bonding (stress bonding). He's only four months old...if the problem continues when he's an adult, I think I'll take them both to the vet and she if she has advice. Also, so she can re-examine Winston, and confirm (again) that he had been neutered. I'm still a little skeptical about it, just because of how quickly his behavior changed.