The Intercontinental is nice. I'd leave about 715-730 to arrive by 800-815 and I think that's fine. This is Mexico, so you know, 15 minutes one way or the other isn't "late."
Customs is in Dallas (no preclear in MTY), and the new customs area in DFW is HUGE if you haven't been there yet. Brand spanking new and clean as a whistle.
Not sure on priority pass at Centurion lounge. Might find something if you Google it?
I'm actually going to MTY myself on Monday-Thursday since I'll be in Dallas for a meeting.