The question always arises as to what the WAS finds so attractive about the OW
Do you mean that nobody has answered you?
Okay,I'll say it. It has absolutely nothing to do about how attractive she may be. It has everything to do with how she is making him feel good. She is making him feel more like a man. She is feeding his ego. She is doing something that you stopped doing when you got too busy raising a family and dealing with life.
I can almost feel the flames over the computer! I know all the things you could say in response, but it still happened. Doesn't mean you failed as a W. Maybe you treated him like a King,but there is something this OW is doing that draws him to her. Count on it.
Now about gift giving. What does gift giving mean to you? If he is still in the house, will there be a time the family opens gifts together?
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!