Does prayer become invalid if the Fatiha is recited by moving the lips only, without an audible sound, coupled with the fear that the letters may not emanate from their correct articulation points?

Giving in to obsessive thoughts and not turning away from them is the cause of your suffering. The cure for this is to turn away from obsessive thoughts and not pay attention to them. Reading aloud is not a radical solution to your problem, even though some scholars have permitted it to ward off waswas. Rather, the optimal solution is to read normally without paying attention to the waswas. With every obsessive thought that you have not articulated the letter from its proper articulation point, say: "Yes, I have articulated it."

The majority of scholars stipulated that the reciter must hear themselves for their recitation to be valid. However, the Malikis, Ibn Taymiyyah, and Al-Uthaymeen disagreed, not stipulating that one must hear oneself. They said that sufficiency is achieved by articulating the letters from their proper articulation points and moving the tongue and lips, even if one does not hear oneself. As long as you are afflicted with waswas, there is no harm in adopting this view. So move your tongue and lips with the recitation, even if you do not hear yourself, then turn away from the obsessive thought that you have not pronounced the letter correctly until Allah Almighty grants you recovery.