The wifi off thingy is not there.
The DNS server for Tubehax has two purposes, one of which is to direct youtube.com to a custom webpage so when the YouTube app opens, it instantly loads the exploit on the hijacked webpage. The other purpose it has is to block the Nintendo update servers (NUS) so if a firmware update happens, your 3DS will never know about it in affect also blocking the eShop as it requires a connection to the NUS to check for FW updates. The DNS does nothing else, and everything else should work fine.
Now that Nintendo patched the YouTube
app, you can no longer use it without updating, which patches the exploit. Updating also requires eShop, which requires you to disable the DNS to use. That said, you don't actually need to update anything (or change wifi settings) as there are other entry points you can use such as browserhax, which has not been patched and likely can't be without a firmware update. You can use
browserhax to install themehax with its homebrew app installer.
There are plenty of
tutorials on here and youtube that explain how to install themehax with browserhax.
