brother, i'm so sorry about the poor husband that still he is thinking of loosing the wife who doesn't deserve such a nice man. he has to understand that if his wife is like this, soon or later but one day will come that the relationship will break between them. i'm also a single father living with my son alone for a long time but my problems were different.
he should not think about that he will loose his wife, infact she will loose him and once she will be divorced than she will know the price of having a good husband.
he should report the police and even if he is on visit visa, he can do everything against their affair.
gud luck brother,
regards,
khalid