Have you tried scraping the bark away in a few places? Just use your thumb nail to scrape a very small amount off. If there is green underneath the tree is still alive. Where the brittle shoots you removed small or large? One of our acer's turned up its toes last year - it was in a spot that was too windy for it and it gave up the ghost. I recently pruned one that was getting a bit too big for its boots.

Sorry it appears to have died. If you replant choose a semi shaded spot out of the wind.