I can't believe the string of upset you have had. I'm really sad for you and your Dkiddies. It's not fair to have this mountain of turmoil. I've gone back to read your old posts and just wanted to say to you to please recognize that you are doing a lot, possibly everything you could, to help solve these issues. Also, nobody knows what will happen, but maybe this is the very hardest parenting year you will ever have. There are always going to be problems with children and some much, much worse than others. I pray that it is just your very lowest point and that you will learn tools that will head off other problems. I hope all the coming years are much easier.
I can only share my own experience with difficult times and don't have any specific experience with the issues you have shared. So, what I will share is that I've finally learned to accept that something really awful, irritating or scary can happen at any moment. I don't control that. I lived a lot of my life fearing that reality. Since I've always made such a big deal out of controlling absolutely everything--including trivial things, it made it impossible for me to accept the truly serious issues came. I always thought, "I work so hard at everything, why????" The bottom line was I was just too hard on myself and too concerned with doing it all perfectly. So, I had to change. What I learned in the process was that I had a huge fear of dropping one of the hundred balls I was trying to keep juggled in the air. I found when I dropped a ball things that were going to happen still did. I've finally learned how to let go of the idea that I had to control everything and how to hand over my fears of how things will be when I do. It's true that there is a lot of chaos with me---appearance, home, extended family, but I've never felt more in control. Learning to accept my limits has been the most liberating experience I've had ever. I wish I knew this years ago. I'm slowly working at the chaos and unlike other times, not cycling through the same failures over and over again.
So, my advice you is to thank yourself for all you ARE doing and stop being so hard on yourself. Most of all, stop looking for the finish line because there isn't one. These issues will pass, hopefully with great resolutions and new issues will replace them. As hard as your issues have been--- and they are very, very hard, you will get through. You are strong and will find answers and maybe when you share here will help us even more than you already have. If I were you I would focus on how completely aware and how on top of your children's issues you are. Other parents do nothing or choose to be blissfully unaware. This difference is what makes you a great parent.
... and about the job? From my own experience I have never regretted quitting a fabulous job. Maybe someday I will find one just as great, but maybe not. It doesn't matter because I know it was the right choice for our family. Ask for a family leave (family and medical leave act 1993) for now to care for a family member. A clinical psychologist can help get that done. Plus, a lot of companies don't give families a hard time when you present an urgent medical crisis and shame on them if they do. You don't have to give specific details and can still work part time.
Well, good luck to you in whatever you choose. More hugs!