I would have made fun of a kid named Atticus by calling him "take-a-piss" -If that's the worst he gets, he'll be fine. Our last name provides more fodder imo.
The slightly unusual name will lead to more teasing and bullying. It will also be unforgettable - which can be handy if you want to be remembered. Since you're handing the kid a three-syllable first name and a three-syllable last name, you might want to consider a very short one-syllable middle name that he can retreat to if necessary. (Biff?) Meanwhile, are you ok with "At" for daily life? We have a neighbour who named his kid Didymus. He still calls himself Did. I just checked his facebook and Did seems to be in the funeral parlour business. Just sayin'
My son "@" will be oozing confidence and power from the moment he breathes his first breath. I'm not worried about him. For the record, my daughter was/is too :)