I wish some of us could say how we managed it Shiela . I found sundowning very difficult indeed.
When my husband was sundowning he often didn`t know me and went out to find his real wife and his real home. That was the most challenging time as well as his packing his belongings in plastic bags. It was easier in the winter when it was dark because then I could persuade him to wait till `tomorrow` because it was too cold or too windy or too dark. The summer was a nightmare which I suspect is what is happening with your husband now.
It's really hard, my husband has sundowning symptoms and I often resort to taking him out in the car, doesn't always work and he can be worse on our return, it's not my home, won't get out of the car etc. but more often than not he is tired when we get back and happy to sit in his chair. Do sympathise and hope other posts help.