"I've been ruminating almost constantly about the unreality of my so-called issues. " Just some random thoughts of mine: your mind is a blessing (you seem very intelligent) and a curse (you seem to get caught up in your thoughts). Some people are not into the "mindfulness" thing. I can't do yoga anymore but I used to do a lot of it. Most classes end with guided meditation. They would have you lay on your back, close your eyes, and breath in a relaxed, steady and full sort of way. Trying to just listen and think about your breath. Other thoughts will creep in, the sort of things you post about. That's OK; you're supposed to just acknowledge it, be relaxed but return to thinking about your breath. The more you do it; the more you sort of train your mind to return to focusing on your breath. When I went through a bad period (ruminating, disturbing thoughts), I sort of did this last week as part of my bedtime routine and it seemed to help. Of course, all the years of yoga sort of trained me to be able to return to this feeling. Anyways, I just saying that some form of meditation might help if you are open to it.
Another random thought (I'm sure your mind has already explored this). The unpredictability of you mother's mood swings may have affected your brain in a "PTSD" sort of way. That kind of thing is more traumatic when you are very young. No, it's not as bad as people who have been abused or in a war zone but it still could have affected you in that sort of way. (Makes you really have empathy for people who have suffered worse abuse, doesn't it?) But, nevertheless, the SH thoughts, isolation, guilt, emptiness, etc. are very real problems. All you can do is try to learn to accept it and work with it. Perhaps you need to consult with a therapist of psychiatric if it becomes to overwhelming for you.
So I hope you are doing a little better this morning and I enjoy your penchant toward philosophical discussion (but try not to allow yourself to ruminate about philosophy so much that you're in utter anguish).