First off, welcome to the family!!! I too am a convert and I had some of the same questions so I can relate to your reservations.
The doctrines of Mary are best understood in their development - scripture does not teach many of them implicitly but they are there if you remember scripture is interpreted by the authority that gave us the scriptures - the church.
Also, most of the Marian doctrines developed with the early Christological (who is Jesus?) debates. For instance, in order for Jesus to be unstained by original sin, His mother must have been without original sin (immaculately conceived). To question one side of that equation is to weaken the argument for the other. Another instance is that the early church had to fight heresies that questioned the dual nature of Jesus (fully man and fully God) - one remedy to the heresies that denied Jesus was fully God was to identify Mary as “theotokos” - greek for “the one who carried the One who is God” or, shortened in our less exact language as “Mother of God.” And so, acknowledging Mary as the theotokos became a test of orthodoxy to determine if one acknowledge the dual-nature of Christ. Again, challenging her as Mother of God is a challenge to the nature of Christ. I think this is a key problem with questions on the Marian doctrines - we do not realize how closely tied they are to the doctrines of Christ and how weakening the doctrines of Mary weakens the doctrines of Christ. So, if someone is attempting to undermine your faith by questions about the doctrines of Mary, be aware of how closely they are tied to who Jesus is. Do not let anybody rob you of these well-thought out truths.
In addition, there is evidence very early on of Marian traditions in the church. Ignatius of Antioch, writing in the early 2nd century, draws parallels between Eve and Mary similar to the parallel Paul gives us in his writings of Adam and Jesus. In both cases, the first Eve/Adam led humanity to sin by their disobedience and the second Mary/Jesus undid that disobedience with their obedience leading us to righteousness. What is interesting is that Ignatius conveys this parallel between Eve and Mary without explanations of any kind - he just drops it casually in his writings as if everybody had heard it before and it was without question - a common teaching in the church. It was a common typological view of the Old Testament which led to other parallels - Mary/Sarai, Mary/Esther, Mary/Woman in Song of Solomon, and so on. So that, with time, a great deal of Marian doctrine was gleaned from the “types” of Mary prefigured in the Old Testament - just as we have found “types” of Jesus in the Old Testament.
You might find some of these books helpful, I know there are many others:
Concerning Mary, Mother of God
On your question about saints - I think you will find Patrick Madrid’s little book, Any Friend of God’s… (linked in that list on Mary) very helpful. It is short and very readable.
fellowChristian posted some good stuff on the Rosary mysteries. You can find quite a few good devotionals that provide similar information and are quite helpful in your prayers. One of my favorites is St. Josemaria’s Holy Rosary devotional, also linked in that list.
