Company Background:
We are a small logistics provider in Europe. A few months ago there's been a change in management and now I'm in charge. I've been with the company for over 5 years and quite young. The previous manager was on the job for over 10 years.
Employee in Question:
Has been with the company for over 10 years. He's old to the point that it'd be a challenge to find a new job.
Problematic Behaviour:
He's constantly in a bad mood due to personal issues. (Relationships / Drugs / Depression(?) / Poverty)
He's not interested in being a part of the team. Doesn't take part in team activities. Dislikes eating lunch together and when he does sit down with the rest never makes conversation, instead checking his phone or solving crossword puzzles.
He just does just a bit less than the bare minimum on the job, which creates work for everyone else. Also totally unacceptable from a buisness perspective.
Every now and then, he's late, which is an absolute no-go in our line of work.
He's very open about his emotional pain, loudly playing love songs in the office, which annoys people.
What's been tried
The previous manager had ongoing talks with him about improvement (for years). I've had two sit-downs with him so far. He improved after the first one, went on holiday after the second one and since he came back 2 months ago it's been the worst it's ever been, that I know of. I don't know if telling him to seek professional help for improving his mental health has been tried. I do suspect he'd never go to therapy, and he doesn't have the money for it.
Tricky situation
I like him personally. Before being a manager, I even had some fun slacking off a bit with him while at work. (I'm all for having a laugh and taking it easy, as long as the performance is there when it's needed)
He has his good days (not so often anymore), where everything's fine and he's a pleasure to work with.
He's impulsive and sometimes angry, but at every one-on-one he's very understanding and promises improvement. It just never lasts.
He'd be best of looking for a new job at which he can stay until retirement. Our pay is less than good and the job requires a certain fitness. Every month/year he waits with looking for a new job decreases his chances of getting one. He knows this yet does nothing.
He says he likes working here and says he's got another 3 to 5 years in him.
What now?
I fear talking to him hoping for improvement just doesn't work.
I can't threaten to fire him, because I couldn't go through with it.
Any answer, comment or suggestion is much appreciated, as I really don't know what to do at this point.