Brett is not any more sensitive to IBUs than brewer's yeast. Is that what you were asking? Brett tends to dry a beer out more which will accentuate bitterness though.
I've had good luck with White Labs Brett C from the 60s into the low 80s. Haven't tried with Wyeast's strain. 68-72 F is safest for Brett.
Probably won't take that long, most of my 100% Brett beers are done in ~2 weeks. As long as the gravity is stable, you are safe.
No need to pitch extra yeast. Brett isn't very flocculent, and it produces carbon dioxide at the same rate as ale yeast.
I was really happy with the way this one turned out: http://www.themadfermentationist.com/2007/02/1st-100-brettanomyces-brew.html Essentially a low gravity saison. Brett C would certainly go well with Amarillo, but that would also cover up a lot of its character. I did a great IPA last summer with Brett Trois, Citra, Centennial, and Chinook.