Am I obligated to follow my husband in prayer despite my distrust of his ablution or his proficiency in prayer, and how can I alert him in case of a mistake during prayer, whether I am following him or not?

Errors in ablution, if they do not violate its obligatory acts, do not invalidate the ablution or the prayer. Following an Imam who makes mistakes in his recitation or an ignorant Imam, and performing prayer quickly if it does not compromise ṭumaʾnīnah (tranquility), do not invalidate the prayer. If the Imam's prayer includes something that invalidates it, then it is not permissible for you to follow him, and your prayer is valid if performed individually. Congregational prayer is not a condition for the validity of prayer, and it is not obligatory for women to pray in congregation. If the Imam's prayer is valid but he errs in Al-Fātiḥah, it is obligatory to correct him. A woman can correct errors in prayer for the Imam or for others. Congregational prayer in the mosque is obligatory for an able man who hears the call to prayer.