Regarding the intercessory prayer, here’s an interesting story in the Old Testament, the Book of Job: after Job’s friends turn against him and instead of comforting him in his afflictions, suggest that Job must be a sinner and that’s why God sent those sufferings on him, God finally speaks and among other things, he tells that Job should pray for his friends (Job Chapter 42).
usccb.org/nab/bible/job/job42.htm
Here’s the quote:
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2 And it came to pass after the LORD had spoken these words to Job, that the LORD said to Eliphaz the Temanite, “I am angry with you and with your two friends; for you have not spoken rightly concerning me, as has my servant Job.
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3 Now, therefore, take seven bullocks and seven rams, and go to my servant Job, and offer up a holocaust for yourselves; and let my servant Job pray for you; for his prayer I will accept, not to punish you severely. For you have not spoken rightly concerning me, as has my servant Job.”
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Then Eliphaz the Temanite, and Bildad the Shuhite, and Zophar the Naamathite, went and did as the LORD had commanded them. And the LORD accepted the intercession of Job.
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Also, the LORD restored the prosperity of Job, after he had prayed for his friends; the LORD even gave to Job twice as much as he had before.”
Footnotes 2 and 3 give the following explanation:
"2 [7] The three friends of Job (Elihu is ignored in the Epilogue) are criticized by the LORD because they had (even though in good faith) leveled false charges against him.
3 [8] Job becomes the intercessor for his friends, as were other great Old Testament characters, e.g., Abraham and Moses, and as our Lord would be, whom he prefigured."
I hope this helps to highlight that not only Jesus Christ, but also Old Testament Saints served as intercessors for sinners, and this practice was in accord with God’s will. I guess the intercessory role of Our Lady and other New Testament Saints, is a logical continuation to that. Perhaps their prayers are more effective than our own prayers, because we are sinners. Thus, God may not accept my prayer, but I can ask Holy Mary (and other Saints and Angels) to pray for me. That’s what the story of Job suggests. To me, Mary is as real as my own biological mother. I know she is alive and she cares about me. I happen to have a very loving and caring biological mother. When I ask my heavenly mother, Holy Mary, I imagine she listens and cares as much about me as my earthly mother. In addition, my earthly mother prays for me daily.

When I was in a difficult situation, I asked my mom for some extra prayers. I never feel embarrassed asking my mom for help, whether it’s prayers or material help. My mom is always happy to help me. So, although I have never seen my heavenly mom, Mary, I approach her with the same trust, because I know that she also loves me. And I’m sure she sees me and watches over me all the time.
When I was younger, I felt no affection to Holy Mary, and I couldn’t relate to those people who prayed the Rosary. But I had something of an eureka moment when I read the story of Mary’s apparition to the Aztec Indian Juan Diego on Tepeyac Hill, Mexico, in 1531 (commonly known as Our Lady of Guadalupe). Here we had these poor Indians, victims of a really gory, gruesome pagan religion of human sacrifice and endless cruelty, and Mary came to rescue them and introduce them to the true God. The God and creator of the universe who, instead of asking the Aztecs to kill fellow human beings and their children as a sacrifice to him, allowed his own divine son, Jesus, to be sacrificed and to become the price for humanity’s redemption. At the time, Aztecs were routinely warring and sacrificed tens of thousands of prisoners yearly, to appease the anger of their imaginary pagan Gods. It is also estimated that they killed one quarter of their own children, again for ritual sacrifice to their idol gods. They were in the stranglehold of a false religion, and Mary came to rescue them. By 1541, ten years after Our Lady of Guadalupe’s apparition, some 9 million Aztecs converted to Christianity and were baptized by Catholic missionaries. I don’t know why God permitted large portions of humanity to stray away and fall into the trap of false religions. But at God’s appointed time, Mary was allowed to appear and intercede for these people. There were also other appearances, e.g. to Natives (Indians) in Colombia. Learning about Mary’s appearances was an aha moment for me, because I realized that she is not some cold and distant figure, but rather someone who cares about us and loves us. Throw into the mix her appearance of Lourdes, 1858, to St. Bernadette. There she gave us a spring of water with miraculous healing power, and many miraculous cures happened at Lourdes. That’s another example of how Our Lady cares about our physical needs and an example of her intercession in our physical ailments.