Regarding your questions on Christianity, we are not very much keen to engage them in argument because for the most part they are sentimentalists and have no philosophy, therefore they become fanatics or dogmatists, and this type of person we cannot change. But if you find some Christian person who is intelligent to understand philosophy then you may argue that if God is unlimited, how He can be confined to having only one son? The son is the representative of the father, and in that sense he is the same as the father, but also he is different than the father. So Christ is speaking in this sense, that only through the representative of God can one come to God. Just like Krishna says in Bhagavad-gita that one should surrender to a bona fide spiritual master, and then He also says that one should "Surrender unto Me." So there is no difference between surrendering to God or surrendering to God's representative, therefore Christ is also saying just surrender to me, the son or representative or spiritual master, and that is the same as surrendering to my father. Accepting the Lord or His representative as one's savior means to render loving devotional service to Him, and in return he will give you all protection. But the foolish Christians they think God is their order-supplier so that simply by performing some religious ceremonies they are entitled to receive all benedictions for enhancing their material life. First of all, to be saved by God means that one must obey what God orders or His laws of commandments. But in the Bible God says "Thou shall not kill," but where is the Christian who does not kill animals and eat? They have changed the meaning of kill to mean "murder," and for them, murder means only other humans. So unless you find out some Christian who is actually intelligent, it is useless to try for convincing them of these points. Simply show them by example that we are finding great spiritual joy in serving Krishna, sell them some literature, give them prasadam, and invite to the temple, and if they cannot understand from the point of view of philosophy, at least they will be able to appreciate our wonderful and enlivening activities and that we have proved ourselves the most upright, moral persons and the best examples of enlightened souls for the general improvement of all the citizens.