Hi London,if you look at the edit tab in qavimator, theres the save as option.This gives you an Avm file, that alows you to go back and modify the pose if its not what you wanted when imported. Below that is the Export to second life button, that saves a BVH file of the pose to your folder. Thats the one you import to second life.
As to the pose flutters, make sure you check on and rotate every joint at least 1 degree. This locks all the joints during the pose, so conflicting default anims can not cause problems. Its also helpful to set the priorety to level 3 or better.
I have never tryed a couples animation, so no help there. As always Google is usually our friend.