Son estranged due to controlling spouse

My son & I were always very close. I have two children, he’s the older one. The one that made me a mother & opened up my world to loving unconditionally and so deeply that at times I was completely awe struck. We remained close until he met a particular woman, married her & became completely enmeshed with her family. I’m leaving a lot out here but bottom line, he’s completely controlled by her and her mother. He lives with her parents, it’s very dysfunctional. If you told me this is the person he’d choose, I would have said you’re crazy, it would never happen. It did happen & now they have a daughter, she’s 3.
I am not allowed over their house, my son has cut me out of his life and he’s also estranged from his sister. His life is his wife’s family & he’s turned into a person that gaslight’s, blames my daughter & I for everything under the sun and plays the victim all while jumping through hoops of fire for his wife and her family. I’ve tried ever which way to approach this. I sought therapy for healthy guidance and nothing changes. I miss the person I used to know as my son. Does anyone have any experience/thoughts about how to remain in a healthy frame of mind as I navigate through life without my son or granddaughter (and they just live 10 minutes down the road from me)
Thank you 🙏