If one was left it would be up under the skin above his testicles, visible and palpable, but not in his scrotum which should be absent. It's not likely though, probably just boisterous pseudo sexual behaviour. It will be directed to you also, if you are a female of 'breeding age', pardon the indelicacy - as my husband says, women have no secrets from a male sheep (or dog, bull, lion, bear.....) If you are a man, then he will see you as a rival for his females. You cannot fairly remove him from being with the ewes, and if they do get in lamb, well, is that such a disaster? The females are young but they will cope.
Have you been hand feeding him treats? If so, stop now, and for the ewes too until he's away. Were he mine, I would simply stay out of the field and not go to him at all until it's time for him to go. So no petting, no feeding. The females will still be friendly once he's gone. When he head butts them, he's just trying to keep his harem together, but as you know that behaviour would only get worse over the years, so definitely good that he's destined for the pot.