I get how hard this all is- If it is MLC-there is nothing you could have done to change his mind and nothing you did to cause it It is His unresolved childhood issues.. The MLCer usually follows a pattern:
they leave suddenly, find a OW sometimes younger or affair down , many are irresponsible with kids, and money- they lie, dress younger, buy cars or expensive gadgets, drugs, alcohol etc.
best to leave the kids out of it as much as possible- they will have to work out their own issues around their dad leaving
but I always felt it is best for them to know that Mom is ok and everything will work sad yes, painful yes- but not their issue or fault we will get through it-
sorry he is bringing oW around for. a pre Christmas visit and hopefully you will not bump into them may want to stay neutral if mutual friends talk about them or meet something simple -not to engage or bad mouth "Not what I want, but I wish them the best"
Just my thoughts any bad mouthing OW will make them closer and move him in that direction usually the R has to run its course and it takes a while
hang in there
married 14 years H 42 bomb 2/07 IDLYA D final 3 /09 M ow D ow