Recognizing "God's Voice"

Why was Cain's sacrifice not acceptable to God? Why did Jesus still offer a morsel of bread dipped in wine to Judas? How can I recognize God's voice in my life? I'm in an abusive family situation and I'm trying to have some healthy boundaries. Can you help me navigate this? Why do I keep making bad decisions in life? Does this mean I'm doing something wrong in my faith? As a believer, should I be dating a Jewish man who doesn't believe Jesus is the Messiah? I suffer from a mental disorder, and I wonder how this fits with the renewing of my mind.