I've read that Gale talks about his other lovers in the romance option, so Mystra wasn't his only lover and he wasn't completely possessed by her. I think making Gale a helpless victim comes from only looking at a piece of history that is dramatic. It's not looking at the big picture.
To avoid confusion: I wasn't suggesting that he was a helpless victim, but that his self-perception was seriously unhealthy and the people closest to him didn't do anything to balance this out. Gale also mentions that he had friends and colleagues whom he shut out once he became aware of how dangerous the orb could potentially be.
