gravexgirl I was trying to figure out whether the steamwebhelper.exe errors in your dxdiag would have anything to do with the Sims 4 issue. I don't think so, but you can test by putting Steam in offline mode. If it helps, it's something about Steam's internet connection; otherwise, it's something else.
If it doesn't help, please create a new admin Windows account and try playing there. Make it local, as in, don't link it to your Microsoft account or any email address. (You can keep saying you don't have that information until you get some security questions instead.) You'll be able to launch Sims 4 without reinstalling anything, but your saves and other content won't be available. That's part of the point, so don't transfer anything to the new account, and don't download content from the Gallery.
The Dance interaction spamming is a known bug:
Game Is Spamming Autonomous Dance Actions | EA Forums - 11888101
But it doesn't sound exactly like what you're seeing. If you think it is the same thing though, let me know.