Why is it so wrong for your D to have lunch with her SD? Honestly what is the problem? I think you need to learn to separate the two different things. I am sorry you were not invited which is where I think the real issue is. Your feelings were hurt and now you are going to stop your D15 from having cantact with the man she knows as her Dad. I think you really need to think about things a little more clearly. I think you need to grow up. It is your perception that he is playing games. Why can't you look at it as he is maintaining a connection to your kids and that should make you happy. STOP FOCUSING ON THE NEGATIVES ALL OF THE TIME. YOU ARE BECOMING A DOWNER. Can you put a smile on your face? Can you look at the positives?
There can be no testimony without a test. I am praying to go through this test and come out the other end with a new and better marriage then before.