Very Upset. Need advice. Ex-wife sent my son to another ex-husband after saying she would take him.

I'm going to give some backstory before getting into the situation. My ex and I have been separated for about eight years and we have a nine-year-old son. She has since been married and divorced twice, the most recent one happening about a month ago, but they appear to be amicable, as we have. My son also has difficulty dealing with change. He does not handle huge life changes well and relies on consistency. So the recent divorce has had an effect on him, but he has mentioned he looks forward to spending time with Mom without her ex.She does deal with mental issues and yesterday texted me saying that her therapist says she should reach out to me and her other ex for help when she is overwhelmed and asked us to take him for the evening. My issue here is that (1) I have caught her in lies where she lied to me to get me to watch our son on her days, (2) she has said very mean things about me that has burned the support bridge I used to offer and (3) I am engaged to someone else and the gears are moving where we are beginning our life together and she does not like the idea of an ex forcing us to drop whatever we're doing to accommodate her whenever she has problems (save for emergencies, such as being admitted to an ER, death in the family, etc.).So, the decision yesterday was since I couldn't watch my son, she was going to send him with other ex-husband. When I told my son this, he started crying. Seeing his reaction, I asked if he'd like to stay with me, and he said no. He was adamant that he wanted to spend time with Mom. I ended up calling her and telling her she needs to spend time with him and after about a 10 minute heated debate and right after I said we'd cancel our plans and take him, she finally agreed.When I picked him up in the morning, I asked what he and Mom did and he told me he ended up going to her ex-husbands house for the night.According to my son, the ex-husband called, asked why he didn't want to hang out with him and suggested taking their PS4, which basically swayed his decision. I think Mom also explained her situation as well, but I don't know how much that swayed his decision. I want to note here that I also explained to him why Mom couldn't see him, but he was still adamant and crying about seeing Mom. In the end, I feel like he was bribed into it, personally.When I heard, I became very mad. I was irate because despite telling Mom that I would take him and she said she would, at the end of the day, he still went to the ex's probably an hour after he was dropped off. I was also mad because I vouched for my son, emphasized that he needed to see her only to have her send him off anyways and have him be fine with it when he was at her house. While I have full custody (meaning I can determine or eliminate visitation), we have a 50/50 arrangement in order for my son to have a relationship with Mom and still be able to see her, and for both of us (Mom and Dad) to have a concrete schedule that we can rely on for personal event planning.We have accommodated Mom for the past few years, adjusting visitation - adding, subtracting and moving days to accommodate her life - but I am at a point where I need to focus on my new family, new life and I need to be able have my relationship with my ex be minimal and not be expected to accommodate her when she has problems, like her and her therapist apparently think should happen. That, in my opinion, is also very unfair.When issues arise in my house, he stays with us, we don't send him off anywhere and we kind of expect the same treatment on the other side. I am at the point where if I find out this happens again, I will most likely reduce visitation. I am ultimately fine with where he goes as long as Mom is with him and if she won't be with him, then it needs to be with family members. I am not fine with him staying alone with her friends or exes when the goal of visitation is for them to spend time with each other. Most of her family members are about 45 minutes away and she has, in most cases, burned bridges with her family as well. The closest sibling of hers won't even talk to her. And my primary concern is that now that she is on her own and by herself, these requests/situations will continue to happen. I've experienced this with with my divorce and her second divorce.However, I understand that my anger and frustration may be clouding my judgment, so I'm looking for insight. Where is my logic justified? Where is my logic being clouded by frustration and anger? via /r/Parenting http://ift.tt/2rjDLd8