1. Well, that's sorted out now, so nothing to worry about, right?
2. Well, a year's worth of testing guns for a gang, plus however much time his foster parents gave him with their guns. I don't imagine they were particularly responsible people, his foster parents. So... maybe a couple of years practice total? He's not going to be perfectly accurate with any weapon he's given to hold, is basically the point being made, hence "as skilled as a fourteen-year-old can be [with guns]".