I hope I understood your question well.
You don’t want to activate/deactivate your pause screen in your Pause WidgetBP, at least I don’t do it that way.
Instead you want to do it in your Character Blueprint, like so:
You can Add “Set Game Paused” and “Set Show Mouse Cursor” too, which will stop everthing and will let you see your mouse on screen and you can disable them in B output of “Flip/Flop”.