D.:
because you have two women who love the same man. One raised him. One fell in love with the man you raised.
The problem with your relationship? You want to control it. You want to relive your youth or your son's childhood through HIS child.
You ripped your daughter in law a new one and you expected her to take it and move on. She has. Without you. Your son cut his apron strings and that drives you absolutely insane. You don't think you did anything wrong in ripping her a new one. Now any apology you give her will be suspect. You have to SHOW her that you accept her into your family and that you will abide by HER RULES. After all, they are her kids, not yours.
You want it to be all about you. You believe that you can drop in on your son and his wife anytime you want. You can't.
You believe you can allow your grandchildren to watch movies that are not acceptable for a 6 year old. You blatantly disrespect your daughter in law on a regular basis.
I've had two mother in laws. My first mother in law was wonderful - she knew her son was NOT perfect and that he was happy with me. When her son couldn't keep his stuff in his pants? She did NOT side with him. She berated him and told him how disappointed she was in him....when we divorced? She kept in touch with me for a few years....
My mother in law now? (now deceased) We had a rough start. However, when she saw that her son was happy with ME? She changed. When she saw that I loved her son, took good (no, great care of him) and that his love was true and returned? She let any anger go over "losing her son" and realized she didn't lose anything...she had GAINED a child...
Maybe you need to realize that you are only losing your son because of YOU, YOUR WORDS, YOUR DEEDS - YOU DID THIS - and stop. Apologize. And make sure you are SERIOUS about it. Then go about earning her trust back. This means following her rules. And seeing that your son is HAPPY. And tell her that. Tell her that you are HAPPY that your son is happy WITH HER....I will tell you that ANY ounce of being fake or false will be seen and you will be shut out. And again - it will be YOU who loses, not them.
Have you considered going to therapy to learn to let go of control, anger, grudges or anything like that? If not. Maybe you should. And you'll find that you can have a WONDERFUL relationship with your daughter in law and son...and maybe even your grandchildren.
Good luck!