You seem really triggered today Mel, hope all is well. To put it in lamens terms, now(because we're in mortal form) our understanding is like looking into a grimy cloudy mirror. But, once we leave this body, we will understand clearly. No one is able to fully explain or comprehend God, because we are finite. You're spot on, we(the created) cannot truly comprehend God(The Creator), much less his will for our lives and the world. You're right also in that we are sentient, He gives us free will, and part of free will is the ability to not walk inline with God's will. How do we then know what God's will for our life is? We learn this through his word. God also speaks to the heart of every individual, His Holy Spirit whispers to the soul of all beings.
On a side note, it's a wonder that anyone would abort a child because it might have a hard life, or might go to an orphanage, when that child could very well overcome all those things, or ever greater have an awesome life despite all odds. Like the drawing, thinking it knows better than the artist, erases the child and all it was meant to be, achieve, and accomplish; only unlike the drawing, who does not have free will, the child is erased from this world forever.
The victory however, is that the murderer, the mother who hired them, and the child, will all most likely dine in heaven together with our Father, Christ, and every other sinner saint amongst the heavenly hosts. God is good :)