What is the duty of the ordinary Christian?
So many questions swirling around, about our relationship to authority in the Church, when that authority is going wrong. We can clearly see the result of dismissing authority full stop. Christ founded His Church and a hierarchy to govern it (this is clearly laid out in the Book of Acts).
But when the Gospel isn't being defended? Then what?
I recommend meditating on this beautiful sermon by St. John Henry Newman: The Gospel A Trust Committed to Us. You can also listen to it here (I don't know what the quality of the narration is). Print it out, take it to your prayer, meditate on it slowly.
Ask for a copy of his collected sermons for Epiphany or your birthday -- they have nourished me for many years (affiliate link),
Your conscience is a real voice within and must be heeded. Know the 10 Commandments and the catechism to grow in wisdom. There are many good catechisms -- this one is short and to the point. A book to help you understand when to obey: True Obedience in the Church.