Ok - so we separated in Oct following realisations that he was passive aggressive and emotionally abusive - thanks MN.
Since then, some short contact visits with DS and mostly smooth. Over Xmas I noticed that another woman has posted a photo of the two of them and commented about her "darling husband" - lots of darlings between the two of them.
I'm not surprised he was cheating, lots of staying out late and evasive behaviour but a bit
that she is already "wife".
Very tempted to do/say something, but part of me thinks best left well alone - any thoughts?