Must a husband have intercourse with his wife if he fondled her and she reached climax, while he is observing a supererogatory fast?

There is no text that obliges a husband to have intercourse with his wife if he is observing a voluntary fast. However, he should fulfill his wife's desire, as this is part of the good companionship enjoined by Allah. He has the right to break her voluntary fast, and he must fulfill her need if she requires it and he is able. Chastifying the wife and satisfying her desire is part of good companionship, and the husband will be rewarded for it.