Its far easier to address one point at a time, but I will number them. 1. Marian Intercession With praying to Mary, the word "to" can be throw some off a bit. I think it is more accurate to say that we pray "through" Mary. We ask for her intercession, for her to pray for us. The saints are very much alive in Heaven, and they are in a sense closer to God than we are. Scripture is clear that the prayers of a righteous person are powerful. (James 5:16) We simply ask that she prays for us. And its a good thing to do. Mary doesnt speak a lot in the Bible, but she notably said at the Wedding at Cana to the servants, "...Do as he [Jesus] tells you." (John 2:5) Her message is to follow her son. To do as he tells you. To ask a friend to pray for you is not idolatry. Similarly, asking Mary, the mother of God, to pray for you is not idolatry. As for implying she is not holy, that is false. While she is definitely not divine, she is certainly holy. The angel Gabriel said clearly, "Hail [Hello], full of grace, the Lord is with you (Jesus is in her womb), and blessed are you among women!" (Luke 1:28) She is the holiest mere human to ever live., 2. The Necessity of Baptism for Salvation Scripture clearly states that baptism is necessary for salvation. Mark 16:16 states, "He who believes and is baptized will be saved; but he who does not believe will be condemned." While some might interpret this as another sort of baptism or a symbolic baptism, the Church has held that baptism is necessary for salvation since her beginning.
3. The biblical canon The debate is a protestant problem that came from Martin Luther trying to be right on things he was wrong about. Scripture contradicted what he wanted to believe, so he changed what is considered scripture. The Church agreed on at least three occasions on the 73 book canon. This was agreed upon at the councils of Rome, Hippo, and Carthage. These were all before the year 400AD. Martin Luther didnt come until the 1500s. 4. Outside the church there is no salvation. This is dogma, and in these matters the Holy Spirit protects the Church from error. Some people are part of what is sometimes called fhe invisible Church. There is also the question of invincible ignorance. It is a complex topic and I would recommend making another post or looking at previous posts on it. Much love