"No query was run" when Contextual Filter is added. Was working before

If there was a communication protocol that encrypts at the very low-level,

There is: IPSec

this would solve the problem of wiretapping entirely and for all.

It doesn't.

Yes - In the Mission Control preference pane make sure that the "When switching to an application, switch to a space with open windows for the application" option is unchecked.

Then for the app(s) you want to behave as in your post: right-click their dock icon and under the 'options' menu item select 'Assign to: None'.