Len-
Wow! I can't tell you how refreshing it is to get something more than “it doesn't work” without having to ask “tell me more!” Yeah, it does seem like a lot, but then I can't exactly throw stones. I live in a glass house, too!
Okay, it does seem that there was some benefit from turning off the Wi-Fi. I do feel like I need to make sure of our terminology, though. To turn off Wi-Fi, we are using either the Wi-Fi icon in the menu bar, or the appropriate entry in Network Settings. The reason I make the distinction is that you mention ethernet, which is actually 10BaseT, 100BaseT, or gigabit wired connection, with ethernet referring to the communication protocol.
Back to the grind! Everything looked fine with your report, however I did find that I need some clarification about why you're running both the 2.4 and 5.0 GHz connections from your Mac? From the rest of your description, I gather that there is only the one Time Machine router on your home network. I understand why it would be running dual band. What I don't understand is why your Mac is connected to both bands.
Again, I'm not throwing stones. I run both bands on my network, as well. Mostly because, due to some bit of unknowable “Cupertino Logic” the iPhone will connect to 802.11n, but only on the 2.4 GHz band. My Mac is connected via dual-band to the 5.0 GHz access point. I do run a backup ethernet connection to the router, since there are times in my work when a slow connection *****, but no connection is very, very, very bad. This is called “redundant networking” and is really the only effective way to plan for a failed Wi-Fi connection. Once again, we delve into the mystical arcana which is Wireless Networking!
You will get the maximum speed from your dual-band connection by setting the bandwidth at your router to either “auto” or “40 MHz,” and connecting your Mac to the 5 GHz access point. Concurrently connecting to the same router, either by Wi-Fi or ethernet, will not improve throughput (network speed). Why not, I have no idea. It has long seemed to me that the bottleneck was the wireless transmission, and that “doubling up” the connection to the router should allow double the connection speed. Unfortunately, it just ain't so. So, unless there is some other compelling reason that you're running a Wi-Fi connection from your Mac to the 2.4 GHz access point of your router, I suggest you remove that connection from Network Preferences and see if it doesn't improve the situation with your mouse.
Cal