But having a tritone interval in the blues scale isn't the same as having it in a chord.I could be wrong here but I think the basic pentatonic minor scale doesn't have the flat second added to it. It's still practically the same blues scale. I use that scale a lot and the tritones are great for pull-offs, hammer-ons and bends. A lot of Heavy Metal riffs are built around those added tritones. Electric Funeral is a great example of this.
You don't usually play all notes of a scale at the same time.
No the basic pentatonic only has 5 notes (hence the name...).