Nanban, I recognise the place you're in at the moment. You've tried everything. You are exhausted with it all. This young woman seems to be enjoying the control she has over you, and by making sure that your son and the children aren't contactable either, she's keeping control over the situation, having you dangle by a thread. It's a horrendous situation, and it's not going to be sorted overnight. You're 'grieving' a loss which is caused only by her spite. Would you be able to take a little control yourself, though? Perhaps by accepting that for the time being, things are going to be as they are, and by making an appointment with your GP, explaining to him/her how family problems are making you feel, and ask for a referral to a counsellor. I had to do this last year when a really bad situation blew up in my family. I couldn't cope and had to go to the GP because of quite awful panic attacks. He referred me to a counsellor who was very helpful and helped me come to terms with the situation. Although you 'grieve' and worry nothing is likely to change just now. If you can take control of your own feelings you're starting to win the battle that this young woman has brought about. I'm thinking about you and hoping so hard for a good outcome for you all.
xx