Just been reading your thread and I have been in your wifes shoes. Out of respect for my h I distantanced myself as much as possible to OM W. H told me he wanted no contact unless through hm and I understood that.
OMW and my paths crossed at sport but I tried 100 % not to be in a position where we talked. Why can you not tell her that you dont wish her to contact at all. IMO it is not an unreasonable request. Dirty texting is stepping out of the boundry of the Marriage. i consider it an affair.
Are you ever going to be friends with these people again - I dont think so. stop any contact with the entire family.