I am deeply worried for you, spacebunny, and am glad you have reached out for connection and help. There are so many elements--the mental illness, the abuse of alcohol, the suicidal threats, the narcissistic wall of silence--that I think that as long as you stay in this isolated situation with him, you will yourself be so mentally broken that you will not be able to make good, rational decisions.
If he has Bipolar Disorder, there are books by Kay Redfield Jamison, a psychiatrist, about her experience as someone with that disease. You might take a look to inform yourself better. And it is common that a person with this disorder is unwilling to take medication.
His threats of suicide are similar to those of persons with Borderline Personality Disorder, and in that illness people also have major mood swings, erratic behavior, and abuse of drugs and alcohol. There is a book called Walking On Eggshells. People with this disorder usually refuse to go to therapy, so treatment is often impossible. You might look at this book to see if you see him in it.
It is possible he is not addicted to alcohol, but is simply abusing it in his periods of mental chaos and instability. AA may not be of help to him. Time will tell.
If you have health insurance, my advice is to go to a family physician, tell the doctor what you are dealing with in your life, and the doctor may make a medical referral to a counselor for you for trauma, the sessions probably covered by insurance for 6-8 weeks. It is likely you are by now suffering from PTSD.
You really can do nothing for your husband. He has to have medical treatment. People with Bipolar do commit suicide sometimes when they are on the depression phase and this is impossible to foresee. But if he is threatening to kill himself at a given time and place, you should call 911 for a mental health crisis team to intervene.
I hope others here will be able to offer you some insight from their own experiences. I'm so sorry you are suffering.