Dear Anzee~
I'm sure for you this is a never-ending nightmare, and that outside agencies have a simplistic and impractical approach to things, in fact often push to have things "their own way".
In the long term overall they may do some good, though they may well do harm as well, something you have pointed out before.
Over the years you have shown, despite you poor regard of yourself, that you a loving mother. That you have an excellent grasp of what is going on and act sensibly (and yes that includes all the things you have blamed yourself forr. No, I'm not going to repeat them here, we have talked of them before. Please just try to believe in your circumstances no one could have acted better.
Your kids are settling down, which is a huge bonus, and you did mention (forgive me if I got it wrong - that you have someone new as a friend. All that of course under the cloud of your ex's threatening presence. Maybe inch by inch you are getting there
May I suggest that even though you have the strong temptation to say to Child Protection that all is good this is not a way you will be happy with in the future - even if it does make them go away right now.
OK, so setting out in detail what has happened may well be beyond you at the moment, and fear they will make matters worse holds you back.
Is it possible to steer a temporary middle course and simply say you do not wish to talk to them at least for now as past experience leads you to believe there is a possibility they will make matters worse. Also that your mental health is very precarious and you are not up to anything further now.
Then leave it at that. No explanations, no further talk now.
This approach (they will no doubt want to argue or ask why) does not close the door for the future, does not exonerate your ex and allows describing the truth later on if you need to to be effective.
I know what I'm offering as a thought for you to consider is not an easy thing, however you have done many seemingly impossible things in the past and still very much have my admiration.
You may also like to consider either having someone with you or just handing over a note.
If I remember last time we spoke (sorry if I've remembered wrong) both you mother and sister were difficult and did not support you - is that still the case?
Also may I ask if you do have anyone to support you, not prod you into ill-advised actions, but listen with sympathy and care?
I hope to hear from you again
Croix