With regards treatment, she has been ill since approx the 1980s but no one picked up on it until approx early 2000s. She's had on/off depo injections since then. Initially the injections made her almost zombie like where she had very slow thoughts and movements but it dulled her delusional thoughts so that was a positive.
Each time she came off section (because she fought it continually and as with your ex she presents very eloquently, calmly and is highly intelligent so tribunals were sucked in by her) she stopped having meds until she deteriorated so badly she was again sectioned and the process restarted.
Sadly, this time round the injection appears to be having no effect at all and she was sectioned less than a week after the tribunal deemed her fine to be discharged 
There is an oral med which is apparently better but she's never been able to try it as she cannot be trusted to take it without supervision.
It's taken a good few years for her to get to the current state of complete deterioration, but now we feel beyond powerless and when she's not in hospital I get phone calls and messages from her or other agencies (including police) so it's relentless
I don't say this to scare you, but I think it's important to have someone point out how damaging and absorbing someone with this condition can be as you truly need to give yourself permission to step back from the situation.
One thing I've learnt is you have to learn to force MH services to act else you'll get nothing. We've had to learn to use key words where relevant to get our point across and force action and to have bullet points on the specific things that evidence she poses a risk to herself or that her actions are making her vulnerable. So instead of saying we're worried, we have to say we are worried there are safeguarding issues and then list them (this is a key buzzword which reminds agencies they need to think carefully before dismissing what you've raised).
Dealing with MH services is frustrating and infuriating so I feel your pain.
My mum is so focused on my dad still (she's not seen him in at least 4 years) that she thinks he's the mastermind behind all the actions of the other figures of her imagination. She's made false (awful) accusations to neighbours and goes on strange imaginary missions. If dad was still in her life I imagine it would be worse as he'd get lots of hostility and verbal remarks. As your ex is so focused on you I strongly recommend you remove yourself from interactions as much as possible
I don't want to sound too 'doom and gloom' but there are lots of parallels in what you wrote so if I can save you from mistakes we've made and from unnecessary pain then it's worth it