Sorry just have to disagree. A tritone is a dominant or leading tone function. It may occupy a Ib7 position or any position, but it's still a dominant function. As for m6, it's a dominant 9th with the 5th in the bass. (a very common trick) You can't play a pure Ionian or Lydian scale over a dominant chord without a major clash. (unless you have deep experience in bebop and modern country.)