1) Why has god hardened my soul? He had a believer before.
We first have to examine whether or not we have quenched the Spirit of God by our non-repentant lifestyle. If this is true, we have hardened ourselves and have grieved Him, and He has turned His face from us, until we are willing to take up our cross once more. If we are truly walking in a repentant lifestyle and not abiding in sin, but we find ourselves seemingly far away from the Lord, we have to remember Jeremiah 17:9 -- "The heart is deceitful above all things and desperately wicked, who can know it?" Feelings and emotionalism should never be the foundation of whether or not God is close to us, or whether our soul is hardened. Sometimes the Christian lifestyle is hardship, sacrifice, pain, martyrdom. It is not always easy. We will not always enjoy it. But we must remember, there is no valley that is not for our endurance, there is no fire that is not for our purification, there is no pruning of our dead branches that is not to make ourselves once again fruitful... we sometimes find ourselves feeling tightly cornered on all sides, in utter darkness, tossed to and fro by the ebb and flow of life... but those were the exact conditions Moses was in as an infant in a basket, the Lord uses unusual conditions to manifest our calling and our destiny in Him. Amen.
2) If god's plan was for me to be a Christian, then an atheist, then die and go to hell, why bother?
The Lord never plans for us to be atheist. He desires us to have abundant life in His name. We ultimately become atheist in one way only, and it stems from the sin of pride: We exalt our own logic and reasoning over the word of the Lord. Once we allow our personal understanding and our egotism to become an idol over what God has said, what hope is there for us? We will be delivered over to a reprobate mind, satisfied only in itself and its own reasoning, because we have chosen it against His written word and the testimony of His holy ones.
3) How can I possibly have free will if the only choice is follow god or burn in hell? That's not free will, that's a dictatorship.
This question is easier to answer when you fully affirm yourself in the understanding that God does as God does. He shall do whatsoever He chooses to do, and we are subject to that -- the real question here is do we truly believe that He is God? If so, we trust in His mercy and His judgment alike. If you do believe He is God, it doesn't matter if hell exists or it doesn't in your mind, you trust in His will, and you seek to be with Him, and to pull others away from that end.