But I don’t think I’ve ever private messaged any of his friends, or will ever need to.
Exactly.
This is the point.
There is no need for this.
I don't know any men who do this.
(And as you said, he's even continued after the inappropriate episode).
Best case scenario, he has a compulsion for female attention - he's using your friend/ acquaintance/service provider circle to try to get it. Absolute best case scenario.
(And he doesn't give a fuck whether that's uncomfortable for you, or what it looks like)
Worst ... He'd potentially shag anyone he's attracted to if he had the opportunity, and he's using your friend/acquaintance/service provider circle to try to fish for that.
You say he works away, I'd wonder what he gets up to (or would get up to given any chance) when he's working away tbh.
I'd also imagine that he's either said something to your nail tech suggesting your marriage is not secure ..or she has drawn the conclusion from him contacting her completely unnecessarily that he's on the lookout for a new woman/or at the very least trying to cheat, and she's hinting that.
It's a very strange thing for a service provider to say to a client ..... Seems like she's heavily hinting to you. She's perhaps trying to help you.
(She perhaps even knows from other women that he's doing this to them too. It's a small world).
Even if it's the best case scenario above (attention) ....this is not behaviour anyone should be having to tolerate in a relationship. And I bet it's not behaviour he would tolerate in a relationship.