I hear you - but you did ask how to block the beta build from installing (automatically).
The "other" option, still in the same pane, is to turn off "Download newly available updates in the background", so updates don't even download, unless you choose to download.
You would have full control over doing that when you are next ready.
I suggest that it could be worthwhile to do a reinstall of the current Sierra version. That might leave you with a safe return to the beta, if you want to try again.
You don't still have that Kaspersky stuff installed, do you?
