No one is going to criticize you for getting checked, for your sake and Gavin's. I am happy that the tests turned out good.
Don't beat yourself up so much, you apologized a lot to Dwayne, I don't think you needed to. Standing your ground and asking the questions that you did, even if it made him angry, does not lower you to his level.
You did the right thing and asked the right questions, I think he reacted the way he did because he knows he put you in that frame of mind, and maybe he isn't that happy with himself.
Good luck with Gavin.
Ex.