Hi again,
Much of what you write mirrors what happened to my adult stepdaughter with BPD. Though she was always a sensitive, moody, (over)reactive and hesitant/avoidant child, her BPD behaviors and general dysfunction didn't emerge until she went away to college. She lost all her friends. She self-medicated with marijuana. She'd get into trouble (with eviction, failing classes, quitting jobs, dropping out of school), but lacked resilience and couldn't find solutions by herself. She had suicidal thoughts and attemped suicide multiple times. She had raging outbursts directed at her family, blaming them for a terrible childhood and all her current problems. Like your son, she's obsessively worried about finances; the irony is, she took on zero student debt, so technically she started adulthood financially much more comfortable than most people, myself included.
I'm going to repeat parts of a prior post here about a BPD daughter to help explain what I think was going on. In essence I think it's a combination of immature emotional skills, unrealistic expectations (rooted in black-and-white thinking), plus shame and fear about "adulting":
I have a few theories about BPD behavior, and they might clash with some of the classic recommendations on these boards (e.g. validate the feelings, not the facts). First is that your daughter is blame-shifting. She's not really mad at you for what she's accusing you of, even if that is what she THINKS she's mad about. I bet what's really bugging her is fear about the future. She knows she's an adult in age, but she still feels like a dependent adolescent, and it's killing her. She doesn't really know who she is (she lacks a stable identity), and she doesn't have stable relationships (friends, co-workers, family, romantic partner). Without the high school routine that was forced upon her, she feels rudderless. Is she having trouble in college, and does she have a hard time finding (or keeping) a job? Has she lost her friends? She is discovering that she's not functioning well as an adult, and that makes her SCARED as well as inferior. "Everyone else" seems to have an easy time making friends, finishing college and/or working, whereas she completely falls apart. This induces in her a deep SHAME. Rather than take setbacks in stride (failing a class isn't so bad--she can retake it; having a fight with a roommate can happen, but apologizing goes a long way; getting fired isn't the end of the world, there are a million other jobs out there), and rather than take some responsibility (I'll never make any money or friends if I stay lying in my childhood bedroom all day), she regresses in AVOIDANCE. What does she do? She dredges up ancient history from childhood and blames her dysfunction on that--terrible/unsupportive/abusive family members, they are the ones who are making her dysfunctional. This thought pattern makes her MAD, because she doesn't have what she wants today. When she sees you, she sees an opportunity to lash out and unleash all this anger and frustration onto you. If you're up for listening to her, you become her punching bag. If you try to validate her feelings, then I think you're giving credence to the notion that a terrible childhood is the central problem. However I think it's not--I think it's just blame-shifting. The accusations against the family serve to AVOID dealing with current problems and taking responsibility for her life and her decisions. That is simply too scary. She RESENTS you because she still NEEDS you desperately, and it's killing her inside.
On top of that, generally speaking, her expectations are totally unreasonable and unrealistic. I think this is rooted in adolescent or childish thinking patters. She's impatient. She's demanding. She still expects adults to over-function for her. She still expects to be the center of attention at all times. She expects too much devotion from friends. She pines for the amount of leisure time she had as a child--long summer vacations, ample holiday breaks, a life mostly devoid of responsibilities and pressures. She wants to make decisions, but if something goes wrong, she expects you to face the consequences and "rescue" her, because you "owe" her. Now, when she was a kid, this was normal. But now that she's an adult, she's having trouble adjusting her expectations, and at the same time, her childish expectations simply aren't being met, which sets her up for constant disappointment. She still probably expects that you continue to pay most or all of her living expenses. She's resistant to doing adult administrative tasks, and she's frightened because she doesn't necessarily have the know-how, either. She's afraid to ask for help, say from a friend or an employer, because she'd be "exposed" for her lack of knowledge, for the fraud she feels she is. She wasn't really prepared to do autonomous, self-guided study in college, or to figure out how to apply for jobs, or even how to accept coaching from a supervisor. Any "criticism" would be taken personally, and she'd completely fall apart. I bet she hasn't really embraced the notion that she's responsible for herself now, because she's probably blaming you, full-time. Let me guess, your daughter says she suffers from anxiety? My bet is that's because she feels incompetent, inferior and scared. She's so afraid of a failing and a little stress that she gives up before she even tries, and to cope, she's lashing out at you. Does this sound familiar? If it does, it's because I've lived though it, all of it.
Anyway, I have some thoughts about your last post. First, the license--is that a driver's license? If it is, my guess is that your son feels shame about not having one yet. He can't put things in perspective (maybe he didn't have a car available to practice on? maybe he was busy with other things? maybe he was saving up for classes?). Perhaps he thinks "other people" will think less of him for not having a license already? He lets all these negative, extraneous, irrelevant thoughts inhibit him . . . when the central issue is probably just fear of failure. That would be indicative of BPD black-and-white thinking. So what if he fails at his first attempt? Millions of people fail their driver's test, and so what? They just have to get more practice and try again. I'd say, if he has a graduate degree, he's probably way smarter than the average driver. But his negative thinking gets in his way. If he's like my adult BPD stepdaughter, the go-to coping tactic is AVOIDANCE. But avoidance just delays the problem and often seems to make it worse in the long run.
Second, you ask about family therapy. My gut feeling is that therapy with you might become a raging blame-fest. Like I stated previously, it might lend credence to the notion that his "horrible" childhood is the source of all his problems. Whilst he might have some unresolved issues there, my gut tells me it's not the main issue for him right now. I think that therapy sessions which revive ancient grievances might only serve to magnify them, and not help him get past them. Maybe I'm off base here, but I sense that repairing the parental relationship is more likely to happen if he addresses his core BPD issues first--emotional reactivity, fragile sense of self, feelings of worthlessness, etc. If his life is looking really dysfunctional right now, my sense is that he might not be "ready" to repair things with you yet, and that he might need to focus on therapy for himself right now. I'm not sure, but my sense is that there would be a better chance of relationship repair if your son had gotten his act together and had a more stable, positive adult "identity." I think a sign of that would be repairing some relationships with friends first, where the stakes are lower. I don't know if that perspective helps? At any rate, I'd recommend that you do not try to arrange any therapy for your son. If he wants you to attend a therapy session, then he should be asking you.
Just my two cents.
yeah, well, me...'you're never there for me when I need you!'...all the while calling in to work to take care of her when she's sick. Helping her move out of her ex fiance's house which was awkward as heck. After her grandma's passing I went to that woman's apartment a dozen times and went through all of her belongings which was also awkward. Helped her dad move out of his apartment. Drove her everywhere. The list goes on. But, I was NEVER there. 
