Thank you for updating OP, & please believe in the strength of feeling that has been generated by your thread.
Nobody is looking to scold or berate you or add any more to your appalling stress. Some of us have been where you are, & understand the fear, the mindfuck, the minimising & excusing of the Ex ... and we are scared for you.
With that in mind, may I urge you to cancel your solicitor letter? There is no point in tipping him the wink that you may be taking formal action. When you do - & you really must, this man should NEVER step foot in the marital home again - it needs to be with the full knowledge & support of your local cop shop.
I understand the feelings you may be having of wanting things to appear "normal" for the kids, with their dad able to pop in & out of your home with them. But he seriously must be prevented from doing so again. Never mind how HE feels about that. HE forfeited any notion of being tolerated in your & the kids' home when he cold-bloodedly planned for & placed a surveillance device in it. The kids dont need to know about this, but what they DO need is a mum who knows how to establish & protect her own boundaries.
Please take PP's advice upthread to heart:
You might have the camera, but he has the footage. That could go anywhere. Please let the police go and deal with him, don't let this get any worse for you. A solicitors letter would only warn him to cover his tracks. He wouldn't have time with a knock on the door from the police.
You can do this OP.
I spent 5 months in fear of my life, not sleeping & shaking so hard any chair I sat in rattled. If you had met me then, you would not recognise me now.
I may not have survived without my ace, spectacularly knowledgeable & effective lawyer. I have not written that previous sentence to scare you, but to BEG you to listen to your lawyer. She sounds like she understands the implications & potential ramifications of your situation.
Please ask her to cancel the camera letter, & instead liaise, via her if that helps you, with the police.
Stay strong, stay safe, & be proud of how far you have come already in splitting from this coercive controller.
And now take the formal & necessary steps to remove his influence over you, just as you removed him from the marital home. He needs to know, not only is the law on your side, but that you will not be bullied or manipulated in not using it to stop him in his tracks. My ex, too, felt the law did not apply to him. He stopped his death threats once he was made to realise it did. Yours needs to realise that he has threatened you by his illegal invasion of your privacy - and he needs to know that you know that too, & will use the law to protect yourself from today onward.
We're here for you when you are ready to update OP. Try to give yourself a relaxing evening & as much of a break from this overwhelming thread as you are able, tonight. Tomorrow is a new day, & with support, you will cope. Tomorrow, you can call your lawyer & the police & take proper formal steps. Tonight ... take it as easy as you are able.