There have been many movies where the father, in your position, has made diabolical threats to the young cretin & I'm sure you can find inspiration there. The cleaning of the 45 sounds good, but if you can't arrange to do that in front of him maybe lots of remarks about pistols, tough biker gang rituals etc. may have the desired effect.
I'm sure there's a joke in here somewhere about ATGATT for your daughter but I didn't want to offend your sensibilities

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Have faith, I'm not sure in what, but have faith!
DaveB.