How do I get this creepy old co worker to leave me alone?

I've been working with this man for over 2 years. I remember when I first met him I thought he was a idiot. I tried to prevent him from making a mistake at work and he ignored me and was very rude. I remember saying he wouldn't pass probation and that he was stupid.

For context I work in a very large busy warehouse with hundreds of staff so you don't always see the same staff everyday.

Somehow he managed to pass his probation and he ended up getting the same rota as me which only has 3 other people on so now I see him everyday.

I decided I'd be nice to him and we started with mainly just small talk by the clocking in machines.

2 years on I'm one of the only people who talks to him at work because everyone else can't stand him. I didn't understand why to begin with but I'm slowly realising he just complains a lot, is rude, entitled and lazy. He has no one at home and doesn't talk to any of his family due to a falling out.

I didn't really realise it till someone made a joke about him being my work husband but a lot of people have said his behaviour around me makes them uncomfortable and that he's abit creepy around me.

As soon as people told me this it really opened my eyes. He's always asking why I'm talking to someone and what I'm talking about. Acts jealous when I talk to younger men and accuses them of having a crush on me. Follows me home and talks to me. Wants me to know were I'm at all the time. I can't walk past him without him stopping to talk to me.

Tells me all about his personal life, tries to make fun out of me, listens in to my private conversations with others etc.

I'm also a union rep at work and I was having a private conversation and he was listening in. He's not a union member so any union issues I can not speak to him about and I've been told by my boss to tell him still a lot of times. He got the wrong end of stick whilst earwigging and wanting to get info off of me I told him I couldn't tell him and he got really nasty.

Updates
6 mo
Now I've lead him to believe without actually saying what he thought he overheard was ture and he's gone spreading it around the warehouse. I said it's no one else's fault but his own if he's made to look a idiot he shouldn't be listening into private conversations
How do I get this creepy old co worker to leave me alone?
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