What should the worshiper do if the Imam bows while the worshiper is reciting Al-Fatiha or a Surah, and the worshiper stops at an improper pause within it?

If the Imam bows before the congregant completes his recitation, the congregant should bow with him. Avoiding a "bad stop" is easy and does not compromise following the Imam. The reciter should avoid a "bad stop," but he is not sinful for it, unless the intention is to distort the Qur'an and alter its meaning.