It is down. It took Ds and I five solid hours! He worked like nobody's business -- I seriously couldn't have finished without him. I've never seen a six year old stick with something like that, right to the end. Including washing the walls down with sponges and picking up the garbage when we were done. He even used a putty knife quite capably for scraping off the backing -- he gouged the wall once at the beginning, I kept my mouth shut except to say that it would be no big deal to fix it later, and after that he seemed to figure it out and didn't make another mistake with it.
We used a paper tiger, and Diff, in a garden sprayer. It would have taken less time if I knew what I was doing when I started. Half way through, I realized that I could grab on to the bottom edges of a panal, and take the whole panal off in one sheet. Duh. Then I just dealt with the backing separately, by spraying it again and scraping it off while it was wet. Before this glorious realization, I was picking off little tiny scraps at a time and it was taking forever.
We spackled already, and tomorrow we sand and then paint.