I've just read both threads, im going though similar myself.
Of course they are together he has no other option,hes got to be with her to looks like losing it all was worth it, im so happy shes a fucknut, they wont last long so dont stress.
Hes gone nasty cuz he resents you for finidng out and blames you for him being in this shit situation. He wont ever hold himself accountable hes weak and pathetic.
Not sure if your boy is back or not but if he isnt, keep ringing the police and ask for a welfare check. Also if you can bare it let him have him, let him do all the hard work youve been doing he will soon bring him back.
Keep a diary of everything even the smallest of details you may need this in the future. Let him crack on for custardy, court cousts ££££ and youve not stoped him seeing the kids so it will just be a big waste of his money.
Best advice i was ever hiven on here was grey rock him, give him nothing, dont speak or acknowledge him,hes a narcissist he will die lol
Lots say go to a solictor but there is no rush, but lots of companies do 30mins free.
Also stay in the house you have till your youngest is 18, the kids need stability.
I really hope it gets easier but im 12months on and still have to out up woth all sorts of fuckery.
Goodluck