Our Sheikh, what is your opinion regarding a man who held onto his wife after he learned she had cheated on him?

The basic principle is to assume the best of a Muslim, especially one's wife. Accusing her of betrayal is a serious matter that requires verification. If a husband confirms his wife's infidelity through adultery, he must remind her of Allah and the Last Day, and of repentance. If she repents, then so be it. But if she persists, there is no good in remaining with her, and he must separate from her.