Well, I don't really have any advice for the relationship. But, for GAD, I understand.
Take a few deep breaths through your nose when you tense up. Try to feel the breath and put yourself in the moment. Otherwise panic ensues and it is IMPOSSIBLE to be rational once that happens.
All I can say, is try to manage your anxiety, because this type of relationship is like putting gas on a fire for people with GAD.... I know.