I am so sorry for all that you are dealing with and how your stbx is acting. You are a great lady and deserve so much better.
I understand the hurt from losing the in-laws. My MIL always told me that I was her daughter and the smartest woman x had ever been with. When I left xnpdwh she was so upset to learn that he cheated on me since his dad cheated on her for 20 years. We continued to be close until xnpdwh started lying to her about me. She suddenly told me that it was best that we get divorced. I tried to call her on her birthday and mothers day but she would no longer take my calls. It hurt me so much because she was the mom I never had and I called her mom and she always sent me cards that said 'my daughter.'
I should have been prepared for it since in her eyes x was 'Prince X' (that is what his sis and brother called him) who could do no wrong, but I thought she would stand by me after all his dad had done to her. If she hasn't been in her 80's I might have sent her proof of all the cheating and his admitting to threatening my life. I loved her too much to hurt her like that though.
It will get easier with time but you will always wonder how they can do this to the kids or grandkids. My heart breaks for my granddaughter who adored the x and her GG.
Please post as much as you need to as we are all here for you and one (OK, a lot of us) of us has BTDT. We are here to help you as we were helped by the great people of SI.