Is it permissible to inform the husband of the the true source of food after disobeying his prohibition against eating from a specific person, in order to atone for not telling him the truth out of fear of his anger?

The Shariah obligates a wife to obey her husband regarding conjugal matters and their related issues. You are not sinful for disagreeing with your husband on this matter, but it is better not to express disagreement to maintain a good relationship. Lying is forbidden, but it is permissible for spouses to lie to each other for a benefit, and "Tawriyah" (equivocation) is better. Therefore, do not tell your husband the truth about this food, and if he asks you, use Tawriyah.