Are actions accompanied by the fear of showing off, such as improving one's voice in prayer to evoke the family's reverence, considered showing off (riya') that invalidates the deed, and in this case, is it better to lead the prayer (imamah) or be led (ma'mumiyyah)?

You should have responded to the call to prayer and prayed in the mosque with the Muslim congregation. Do not pay attention to the whispers of Satan about the mistakes of the people of the mosque or hypocrisy when leading the prayer. Ignore these whispers and strive to attend the congregation and attain the reward. We advise you to constantly supplicate and distract yourself from these whispers, and to consult a trustworthy psychiatrist.