He literally offers to sacrifice his own life, immediately upon hearing the plan to sacrifice him. He is also literally that strong, prior to his rejection by Mystra/unfortunate accident. He's not lying.
stay in your lane
He paved that lane.
His Approvals are all tied to good acts. He respects caring for and defending those weaker than him. He supports acts of charity. He supports honesty, and humbles himself before the entire party up to and including being willing to leave over his condition.
There is no way to paint Gale as anything but a good person.