Thank you for sharing this heartbreaking story. None of this is your fault - none of it.
I belong to a men's support group related to addiction recovery, and also to a caregivers' support group for those caring for a loved one recovering from traumatic brain injury (my wife, in my case). Both these groups have taught me that I must not be a tough guy. Tough guys (and tough women) hold back emotions and work hard to avoid showing their feelings. Fine, until sadness and desperation become so overwhelming that a tough guy would rather make the ultimate sacrifice rather than letting his wife / best friend in to explore those feelings and help find a way together. Still, as an introvert and a born tough guy, I can sympathize 100% with your husband and his desire to handle it all by himself. And his eventual feeling of hopelessness.
Thank you for this great article and I do hope you and your sons will draw strength, courage and empathy from the hard journey you're on.