Paul-a-Bipolar

First off, let me say you have my sympathy for all the suffering you, your husband, and, well, I guess everyone else in your son's orbit have had to endure. To let you know where I'm coming from, I, too, am a rapid-cycling Bipolar type II. I believe your son is one, as well, if he has never been delusional, or has hallucinated (except drug-related episodes) and has experienced long periods of severe depression. I, myself, have been hospitalized five times over the years. I'm "high functioning" right now due to a myriad of different medications I take in amounts which are always changing. Also, I have therapy regularly. I always take my meds and always attend regular therapy. I have known many people exactly like your son and many families in your same situation.
This may be difficult to hear, but, you are hurting, not helping your son. You must let him hit the ground, i.e., rock bottom, if he is ever to stand on his own two feet. You and your husband should have drawn personal boundaries long ago and not let him cross them. Don't give him money. Don't try to solve his problems. And, don't give in. That's what they'll tell you at the hospital. Pay for the therapy he regularly attends, sure. (Pay the therapist, yourself.) Pay for the medications that he takes regularly, fine. (Pay the pharmacist, yourself.) If he won't attend therapy regularly and/or won't take his meds, religiously, or, at worst, won't even seek medical intervention, tell him he's on his on his own.
Will he wind up on the streets? I doubt it. He's a very smart guy. He's figured how to avoid that all his life. He can get five jobs in a year? It takes some people months to find one. Quit preventing him from having no choice but to learn to help, himself. If you believe he is a danger to himself, or, others, call the police. He must be taken off the streets, and have a medical evaluation taken. The doctors will decide what should be done. If the police won't bring him in, then, ultimately, your son may cause it to happen, later.
When you confront him and tell him he's on his own, now, at first, he probably won't believe you. When he does, he'll likely become angry and lash out. That will be followed by the emotional blackmail that has always worked in the past. When you hold your ground, he will then, likely, threaten suicide. You then call 911 and say that my son has just said he's going to kill himself. If you're lucky, they'll come get him, right then. If not, he will probably make a suicidal gesture, later. That is a failed attempt at suicide. Then, at long last, he will begin to get the help he needs--when they take him to the hospital and medicate him. Will he stop taking his meds when he gets out? My guess is yes. He'll probably land back in the hospital a few times before he straightens out--as long as you and your husband don't start enabling him, again.
If you are saying to yourself, I could never do that; know that he will always get worse. ("Switching" between mood states is the worst thing that can happen to bipolars. The more it happens, the less likely we are to get better, later. Never delay intervention, is what the doctors say.)
In a hypomanic state, which your son seems to be in a lot, a bipolar has two emotions: anger when he's not getting his way, and a kind of euphoria, when he is. Generally, if you’re hypomanic, you feel good no matter what is happening.
The sad irony is that your son, a drama queen like many of us bipolars who are self-obsessed and enjoy reveling in our problems, is, probably, enjoying life more than you are. Your husband, and yourself, could be suffering from situational depression by now. You both ought to see a psychiatrist, together, to get some therapy and perhaps get some anti-depressants, or, anti-anxiety medications. Actually, you need to go. The M.D. will tell you in a more effective way than I can, basically, what I've just told you, now. So, don't take my word for it, by any means. Go to a doctor and do what he/she says. Go now.