Thank you Dominic!
Dominic suggested in a pm that I reset the nexus before retrying to root it. Since the nexus was only a few days old I decided to do it. Once reset I ran the WUG routing script and it ran with no problems (I had to repeat some steps a couple of times) all the way to "success". I was ready to pm Dominic that he did not need to call me because it was now rooted.
But, when I tested it, it turned out that it was not really rooted and superSU still needed binaries. So I was happy when Dominic called. After his call I reset the nexus a second time and then ran the WUG script again. It did the same things as the first time all the way to success, but this time the success was real and both superSU and Busybox ran fine.
So, I think it was an app on the nexus 7 that prevented the WUG from running and I think I know which one because I recall having similar trouble when I first rooted my android phone. Once I uninstalled that app (without resetting) on the phone the phone rooted with no problem. The app is the anti-theft component of Avast mobile security, and when you think about it, it makes sense. It is designed to prevent the stolen device from being manipulated.
Anyway I am now rooted and happy. Thank you Dominic for suggesting the resetting and to all of you for helping me with your advice and support. I know you probably thought I did not know what I was doing, but it really was not my fault.