Im sorry you are going through this and I'm going to speak to you from experience, police experience. If you present your case to the police in the same way you have wrote your opening post then they are going to presume in the first instance it's a mental health problem. I'm sorry if this is upsetting but I want to be open and honest with you so you get the best out of your post. You sound jumbled up and to be honest quite rambled, which in turn could point to mental health and possible delusions - I do say this in the kindest way possible, I am trying to help.
You speak of things that happened in the past and things that happen now and it's very confusing. You need to focus on NOW!!
The police will want to know exactly what is happening now (the past will come later in evidence gathering, if the case gets that far).
What is happening now, when you say you're being harassed and threatened; are people sending you private messages, threatening you directly with harm and have these people indicated they know your address.
Which social media sites are they using?
Is it name calling or are you receiving genuine threats to your life or property?
How long did you last move and when did they social media posts start again
At the moment are you just receiving messages online or have you had any offline incidents
I'm not expecting you to answer all those questions on here, I'm just saying they are the types of questions that the police should be asking and you should be able to answer. Try and write down everything you want to say before you ring the police.
Online harassment and stalking is very difficult to prove for a number of reasons, especially when you don't know who it is that's contacting you.
IP addresses cannot always be traced as people from all over the world have access to social media and IP addresses can be hacked from all over the world.
I'm not saying you don't have a case btw, I'm just trying to give you a few pointers in the right direction to make the police take your incident(s) more seriously if it does become evident it's a police matter
Good Luck. Feel free to ask me any questions if you wish