That kindof behaviour is probably going to be very hard to break.Im sorry that you had to do that,i had to deal with my RB Dalmation for 9 years.She was always aggressive towards other dogs and was always getting into a fight with my RB Beagle.I couldnt rehome her though,she was my baby.
I dont think you'll have to put him down,unless this behaviour gets alot worse.And i dont think you'll have to rehome him.He's still young so he might grow out of it.Next time you feed them,try to feed Arthur and Charlie as far away from eachother as possible,or even one inside and one outside.
If he doesnt have any other aggressive issues,probably the best way to solve it for now is to feed him in a seperate room,with the door closed,and his crate is a good place too.You could probably talk to a behaviorist also.

Please dont blame yourself ,i could imagine how scary that was