As a recovering addict you know that he is not using at you. It's not personal although it sure does feel that way, at times. You probably also know that he's lying to protect and sustain his addiction. Well enough about him.
That broken pen could have been tossed anywhere, including some place your child could access. Active addicts are not competent to parent because the drug always comes first. Not exposing yourself and your children to someone in active addiction is sound parenting and a healthy boundary.
Boundaries are established to protect ourselves and children and do not seek to control other people. " I will not expose myself or children to someone in active addiction" is a boundary. " You will stop using and seek treatment, or else..." is an attempt to control him. Which approach do you think is more effective at ensuring you and your children are protected?
There is nothing you can do or say that is going to cause him to seek sobriety or compel him to relapse. You are not that powerful. None of are.
You are living proof that recovery is 100% an inside job. Congratulations on your one year mark and for the courage to put your own wellbeing and that of your children before all else. Know that posting your story is an inspiration to others.