Not sure where else to post this. Thanks for reading in advance! Please bear with me it's a long read but all details are needed and necessary
Back story - My nearly 9 year olds dad left me when I was 6 months pregnant, saying we just weren't compatible and that I shouldn't worry as he'll help financially with the child when born and help with buying what is needed before that. (He was actually cheating on me)
Then he changed his mind and decided he didn't want to help buy anything for the baby before DC arrives. I was 24 at the time and not in the best situation financially or in the job I wanted to be in so really needed the help. He then went on to tell me that once baby arrives, he'll be having contact every weekend without fail and if I dare stop that, he will take me to court and make sure I never receive a single penny in maintenance. He's a charmer. When I met him I was in my early twenties and he was 10 years older, I was definitely intimidated by him 
By the time DC was 1, I'd lost count of how many times he'd reminded me that his sister and brother in law were lawyers (you know, just to keep me in check) and I'd lost count of how many times he'd threatened me with court.
By the time DC was two, exp had refused to bring DC home to me after contact, told me he would take me to court yet again if I didn't do as he said, withheld Child maintenance payments if he saw fit, and told me he would be going for full custody, yes - he's that obnoxious I think he believed that could actually happen!
When DC was 3, I had some amazing advice from loads of people on here about his behaviour and we ended up in court to get a formal agreement, which he lost out on of course as I was far too reasonable and allowing exp to have DC EVERY weekend, and chose to work weekends to reduce my childcare costs but when I landed my dream job, that had to change and exp was not agreeable to me spending anytime with DC at the weekends (rolls eyes).
When DC was 5 years old we were at court again because I was now mon-fri 9-5 and exp was being completely unreasonable and not agreeing to give up any weekends with DC, but expected me to work 9-5 Monday to Friday, have all the midweek drudgery of school runs before and after work, homework/discipline etc then never see my child on my days off!!
Since then he collected DC from school early when it wasn't his weekend and played a few other tricks so the last time we were at court was 2018 and what I had hoped to be the last time.
If you're still reading...thank you 
FWIW, when I was working part time and then full time, I would ALWAYS offer exp every single bank holiday with DC as my parents weren't around etc, and often only had two weeks with DC in the summer holidays as that's all the annual leave I could take! It killed me not seeing DC but in a way worked out well for me too as I got to progress my career whilst saving on childcare so although I missed out on a lot of quality time with DC which I HATED, and it really hurt, we are now in a very good and financially stable place.
I cannot begin to tell you the stress exp has put me in over the years and the upset he has caused me. I was thoroughly depressed and couldn't get out of bed some days feeling paralysed with fear and stress over all his constant threats. Now looking back I feel really annoyed at myself for believing him and being SO threatened by him as now I see him for what he is....a narcissistic bully who will say anything to be in control. But I am a lot older and wiser now.
But he is STILL constantly threatening me with court action! It's unbelievable! Last month he wanted to take me to court over a haircut. Yes a haircut! He's not happy that my husband cuts his hair. He clearly feels threatened by my husband but that is his own problem.
I was happy to spilt all holidays between us, so the current set up is that exp gets half of all school holidays plus EOW from after school on Friday til 6pm on Sunday. He also collects DC from school every Wednesday, takes DC for dinner or to a relatives house until 6pm. But still this is not good enough for him. There is one week unaccounted for in the summer holidays where he wants half of. So we're talking about a few days, and he wants to take me to court over this as I said leave it, we can come to an informal agreement at the time (I'm currently on maternity leave and would like to have a few extra days with him for once). But exp NEEDS control and to ensure there is a total split.
The sheriff shouted at him last time for speaking about DC as if DC were a piece of furniture that could be sawn in half!
So now he has text again saying he'll be lodging a F9 paper with court tomorrow where DC get a say in what happens 
He just won't leave me alone. If I looked back on all my texts over the last year alone, I think he's mentioned court at least 5 times. AT LEAST! I'm so sick of it. He has involved the school a few times too and is trying to make me out to be an unreasonable parent, he's now saying DC should fill out this form with his teacher so I don't influence him!! The cheek!! DC used to come home crying after contact saying his dad keeps telling him secrets that he's not allowed to tell me and poor DC was so torn, but this was exps way of trying to crest a wedge between DC and I. So there would be secrets between us (the secret usually being about money, he would tell DC there is 10k sitting in the bank for when DC is older and ridiculous things like that).
It's all really embarrassing and exhausting, not to mention unfair on DC who won't want to do this.
Can I file for harassment? Hoping someone has experience of this. I feel like I can't take a tomorrow of this utter nonsense anymore. I've had more than enough.
FWIW, exp has quit his job to so CMS can't catch up with him, he lives off rental income from his MANY flats which are undeclared and he doesn't pay tax on(I've reported this to HMRC many times, they don't seem to care)
Exp hasn't paid any child maintenance for 6 years now, yet owns a 35k car and takes 4 holidays a year whilst not working and evading tax. Not that this has anything to do with taking me to court, but may give the measure of who he is