The mother of the teen terror accused of punching a Queens grandmother down the steps of a church is defending her son, calling the 16-year-old robbery suspect with a long arrest record an average kid who “does everything he’s supposed to do.” “My son is a good boy,” the 54-year-old mother told the Daily News Friday night at her Queens home. She said she was unaware that her son attempted suicide by wrapping his shirt around his neck and trying to choke himself while in custody at the 107th Precinct station house early Friday. “I’m not aware of him...