Have been reading all this Spook, and don't really know what to say.
This 'love / in love' nonsense. I feel exasperated because it just makes him sound like one of those immature men having a mid-life crisis and not accepting that feelings in relationships grow and change into other things. Solidarity, mutual suport, kindness, all the things that may not be breathless and heady, but create a family. What he is saying is that he does not want to stay in a family relationship. And yet he wants you to maintain his family so that he can pay a visit and experience the thrills from time to time, like a local theme park.
If he wants to break up the family by leaving it, he has to accept that you will need to 'do your thing' and he can't expect you to preserve his family life for him while he goes off in search of responsibility-free relationships.
My own approach would be to attempt to communicate civilly and directly with him, and not make a point of doing things through solicitors - except for anything financial. But that's because that's 'me', and if I can manage it, I prefer the dignity of remaining cool rather than being deliberately awkward or acting out of revenge. if I genuinely couln't cope with the pain of a face-to-face meeting, or if he was bullying or intimidating me, then I would do it through solicitors.
Hope you're looking after yourself, XXXXX