I have been through the process of taking someone to court for harassment.
If his actions cause you alarm or distress or give you reason to feel fearful - it is harassment.
However you have to jump through a few hoops to stop it.
First, go to the police. They will look into what you say. If they find you have cause to feel alarmed, distressed, etc they have to issue an Harassment Warning.
This is the line in the sand. Nothing else will happen to him if this stops him. If, after receiving the warning, he continues to contact you, your employers, your friends or your family - you are in the business of doing him for harassment.
To sue them, the police have to establish "a course of action". That is - more than one event. Everything you told them about at your first visit - that is sort of counted as one event. Anything that happens after that - well now that's two or more events, and you have a course of action.
Beyond this point, once he has crossed that line in the sand of the intial Warning - he is liable to be arrested, questioned, evidence seized (phones, laptops etc) then possibly charged.
Log everything.
Chances are that police harassment warning will be enough to stop him in his tracks. But the sooner you go, the sooner you can get them to swing into action to protect you.
I'd go now, as you have enough stress starting a new job.
My harasser got 5 months suspended sentence - he had sent me over 300 emails, and contacted neighbours, and various other people, with allegations about me. The real point was though, it had to come to court for me to get an order to stop him. Now if he so much as accidentally sent e a spam email - go to jail, do not pass go, no questions asked.
I haven't had a peep out of him in 2 years so it has worked. Good luck.