As a RC, you might be interested in Michael Whelton's Two Paths: Papal Monarchy - Collegial Tradition: Rome's Claims of Papal Supremacy in the Light of Orthodox Christian Teaching.
Also helpful, at least from my point of view, is Fr. Alexander Schmemman's For the Life of the World, which explains the Orthodox view of the sacraments, as well as his Of Water and the Spirit which deals specifically with baptism. And as long as you're checking out Bp. KALLISTOS Ware, also read his other book, The Orthodox Way.
As for the Holy Mother, St. John Maximovitch's The Orthodox Veneration of Mary the Birthgiver of God is a good start. It clearly draws the line between the idea of the "Immaculate Conception" and the (we would say) proper, Orthodox veneration.
God bless you in your reading and prayers.