Running away

My probably-ADHD bf (we both think he has ADHD but he has not been evaluated) is having a breakdown. He is withdrawing and running away, which is his usual reaction when he gets overwhelmed, but this time it's pretty extreme. He is "driving west" for an undetermined amount of time!

He just graduated law school and does not have a job, which weighs on him as his loans kick in soon. He lives at home with an ADHD dad, and his mother and sister, who have their own kind of idiosyncrasies (including being controlling and manipulative). He has two older brothers (that do not live with them), one with ADHD and one with aspergers. The brother with aspergers works with computers, and he has been fired from his last three jobs. He was most recently fired on Monday, and my bf is the only person responsible enough to give him advice and calm everyone down. On Monday and Tuesday he barely spoke to me and was so overwhelmed with the situation at home. Things had been going well with us--we actually had a great conversation about our relationship last week--but the stress was deeply affecting him. He has been living at home for the past two years.

On Wednesday night he got drunk at his band rehearsal, and then told me he was going on a road trip to see the country with his sister, and that they were to leave today (Friday). He has no money, but she has some money and it was her idea. She has been trying to drive a wedge between him and I for years. I know this isn't about me, but her jealousy towards me doesn't help how I feel. I got upset for a number of reasons, in fact I felt heartbroken, and he was snarky and told me I "can't" go with him because I have a job and an apartment. He didn't even act like he would want me to go. This is the complete opposite of the person who was sweet and loving to me just days before. He never plans trips for us, but this is like the 7th trip he has gone on this year (which he rationalized by saying they were for job interviews or to visit family, which not all of them were). He is tired of "answering to me," which I don't understand, because that's the dynamic he has with his family, not with me. He announced to me that he can do whatever he wants. He said he is tired of listening to his parents and being stuck at home, so he "just has to go." Later in the conversation, he had walked to a convenience store because his parents had no food in the house, and he suddenly turned sweet when I changed the topic to his rehearsal and my pet bunny. He was very drunk, and I have never heard him oscillate between petulance and sweetness like that. I asked him to come over last night to talk. He said he would, but not much to my surprise, haven't heard a word from him since our conversation on Wednesday. (Also, last Friday he was supposed to come over, but instead he didn't tell me he wasn't coming and went to bed without eating because he was sad. He said he didn't know why he was sad. He came the next day and we had a great weekend.)

He said he isn't running away from me, he doesn't want to break up, and he still loves me. I believe him, but that doesn't change the fact that his decisions impact me, even if he wishes they didn't. When I was upset, he angrily was like "would you really miss me?" because he thinks we fight all the time (we don't, he was just feeling overwhelmed). I said I would miss him, and asked if he wouldn't miss me, and he said he would miss me. 

I know I can only control myself, and I just need to detach and let go. I could hear from him today or in 4 weeks. My heart is hurting for what he is going through and for myself. I want to know why he is reacting this way, because I can't imagine displacing things on the person I love in such a hurtful way, and then leaving. I know he has a low tolerance for frustration and for feeling bad about himself. I don't understand why everything looks dark to him when he is overwhelmed, including our relationship. I don't know how he can become a completely different person under stress and treat me like this. And I don't know why fight or flight seem to be his primary coping skills. I am tired of this rollercoaster, I'm tired of being told "our patterns" are nothing new when it's mostly his patterns, and I'm tired of how embarrassing it is for me to tell my family and friends. I don't understand why he doesn't let me be there for him, and why he starts treating me like an enemy. I want a supportive partnership. I know I might be collateral damage to his current situation, but how is he okay with letting that happen?

Edit: I thought this post was relevant because of low-frustration tolerance, not talking about feelings, placing blame, etc. I'm in a position that a lot of other posters on these boards seem to be in, which is one of being left to deal with my feelings by myself, and dealing with a lot of unpredictable behavior on his part. He lets us unravel to a certain point and then doesn't want to address anything. I basically wanted some advice on how to deal with this, and was wondering if this is typical of ADHD. If this isn't relevant enough, I will stop posting, but I thought I would clarify my rant first.