Is there a chance to get hpv-16 in oral sex for a monogamous couple if both partners took HPV vaccines already?

Impossible question. Probably not. Especially if both have gardisil (this one fact makes me very happy for you both). So, I am unsure why you keep asking this question. There can be no 100% guarantee for you since there is no test for this in the throat. You have done everything you can today to make sure your are healthy and that this insidious virus is kept at bay in your life.