Has anyone found strategies to help the spouse of a vet who repeats his war experiences, to find support for her experiences?

I don't know if this will help but, you might try contacting one of the Veterans Service Organizations in your area and see if any have a Ladies Auxillary group.
You might be able to get some help from one of them.

There is a fair bit about ex soldiers and POWs reliving their experiences (my FIL was a Japanese WWII POW in Changi in Singapore and on the Burma railway), and a VA nurse should be able to help. However I read your question as being your mother's issues about 'finding support & validation for her own experiences' while he was away. That is trickier. I once asked an older friend about how she and her friends coped locally when virtually all the men were away in WWII, compared with the women in other cities where soldiers on R&R were common (and women's morals were frequently doubtful). I had been reading an old novel 'Come In Spinner', which covered the time and is quite a good read if you can find it. She said that it was different in this city, as one would have been so conspicuous if seen with one of the few men around, and so ostracised within the social group of her own friends. Perhaps raising these different issues might encourage your mother to open up about her own situation, no matter what her temptations, responses and social support may have been. Best wishes to her and your family.

In case anyone interested, here is the Chicago Tribune article. OP, really, talk to a VA nurse. My dad was a POW in Japan. One of longest held. He died at 56. I can only imagine what we might be going through later.
www.chicagotribune.com/news/ct-xpm-2003-01-24-0301240296-story.html

Find a VA hospital and talk to the nurses there. They can relate to what you are dealing with. And might be able to give you some ideas. One of the nurses at my mom's MC was a VA nurse for many years. She dealt with often.

As an aside, the Chicago Tribune ran an article a few years back where ALZ patients, who were survivors of Auschwitz ans similar concentration camps were also reliving those experiences.

My heart goes out to your family.