Is the husband sinful for refusing to be intimate with his wife if she requests intercourse, whether directly or by insinuation, and regardless of whether he has an excuse?

The husband is not obligated to respond to his wife’s request for intercourse every time she asks, whether he has an excuse or not, provided he does not intend to harm her. The husband is not like the wife in the obligation to respond upon request, because he is the owner of the sexual organ, and he may not be energetic at all times. He is obligated to keep her chaste according to his ability and her need. It is part of perfect companionship that he has intercourse with her when she desires it, unless he has an excuse.