What I researched of Barnabas' relation with Angelique is he had a one-night-stand with her in lieu of believing Josette was refusing him. Later on he grabs at Angelique and pushes her away. I see this as having an inner turmoil with his own lust in a unique way. He believed himself to be honourable and was ashamed at this desire which his heart wasn't in.
Later on he accepts the idea of marriage to Angelique (even though she conned him to agree to it) due to perhaps being able to present some justice to her now that Josette was beyond his grasp. Of course, when he discovers what Angelique was responsible for (Sarah's illness being a big, whopping reason) he decides to try for Josette again, or at least say farewell. Josette won't have that, and etc, etc, etc.
(Barnabas also shoots Angelique.)
