You know, my kids were almost killed by my ex (not their father). I can still see one of them being hung precariously over an 18 foot drop onto stairs. For years it played on me. Years. I would see it everywhere I went. Feel it constantly. I think they call that intrusive thoughts or flashbacks. OMG the emotions wrapped in with it. My failure to protect them, my making such a poor choice for a husband. The fact that I called them over that night. It was torturous.
I didn't know anything about trauma at the time. I could no longer deal with my heavy load of responsibilities. Suddenly I felt like the village idiot and couldn't function.
Not trying to take over the conversation - just letting you know I can relate. If I had known more about trauma I would have been able to handle the situation much more efficiently.
I did the following after much research....
EFT (Emotional Freedom Technique) helped me a ton. Find yourself a good practitioner in your area.
Hypnotism - Found a good hypnotist. Sadly, he transferred all of the feelings I had for this situation onto clowns (long story). Then I started having panic attacks over clowns, which was still much better than carrying it with me constantly but not ideal. Maybe a good therapist also understands hypnosis?
I learned how to process emotions and forgive myself for letting it happen in the first place.
If it is any consolation, from my perspective your husband was a lucky man to have the love that he had with you. If I was to die, I would want to know that the person with me cared enough to be doing 100 mph and still try their damnedest to keep me alive until I got the help I needed. We all have to die. It is rare that any of us die with a loved one showing such a deep and loving commitment.
No idea if this is helpful to you at all. If not, please just ignore. I am very sorry for the loss of your husband under such traumatic circumstances.