My ex who cheated with our teenaged coworker will not leave me alone

I (21F) work with my ex (27M,) we dated on and off for almost a year until he cheated on me with a 19 year old girl who also works with us, what’s even worse is he was caught and called out by another one of our coworkers and he dumped me literally hours before I found out. I know I accepted the possibility of things becoming messy when I decided to shit where I eat, but in my defense every time we’d broken up before we were able to stay friends. But this was so unexpected and so cruel any chance of civility is completely out the window as far as I’m concerned.

I would’ve quit months ago if I didn’t love my job, it was a super messy break, but imo I’ve still made it very easy for him. With the exception of the day after our break up when I sent him a message in a moment of weakness calling him a creep and a “waitress hopper,” I haven’t given him anywhere near as much shit as he probably deserves. I don’t speak to him, I don’t look at him, I stay out of his way. We don’t need to communicate to do our jobs effectively, and yet he insists upon it.

He goes out of his way every time we’re there together to try to casually interact with me. He picks up things I’m reaching for so I have to take them out of his hand, he tells me unimportant things that could easily be relayed through a note or another coworker, he stares at me, he does me “favors” that allow him to be around me, he tells me “hi” and “bye.” types of things we’d do during the other times we’ve broken up to remain friendly, though I’ve made it very clear that this time is different and I want nothing to do with him.

All of this I’ve ignored outright, I don’t want to give him the satisfaction of a response, but I also desperately want him to just stop it. It feels like another level of cruelty and manipulation for him to pretend like nothing happened, not to mention it makes me look like a bitch for ignoring him. Especially when other people are around who don’t know the full story. The more I ignore him the more he seems to bother me, it really fucks with me. I don’t know how to get him to stop, all I really want is for him to ignore me back but contacting him to have a serious conversation about it feels like a step backwards.

This is mainly a vent, but I would still appreciate advice from people that have been in a similar situation. If your cheating ex kept on trying to be friends did they eventually give up? Is a conversation where I clearly reenforce my boundaries the only way to get him to stop?