There was no such thing as "atheism" before the Fall of Man meaning "atheism" is one of the many consequences of the Fall of Man!

 Grace is appropriated by faith and by faith alone, no faith no Grace no Grace hell. Faith receives Grace and grace keeps you out of hell and puts you into heaven, easy peasy

 the Bible as we know it is a masterpiece, there's nothing else more accurate when it comes to history, the afterlife, the invisible realm, the creator of the universe and of mankind just to name a few things, but until you're born again the Bible will be come across as nonsense and as fairy tales like it did for me before I was born again and even once you are born again you will need to give yourself over to the Holy Spirit who is the one who inspired the Bible. Easy peasy

 the Christian's greatest enemy is not the enemy the devil but our flesh the old man that needs to be crucified and put off according to Ephesians 4:22 to 24 in James 1:21 for starters

 True Faith and believing always has works, easy peasy, even unbelief has works including doubt and wavering

 According to Calvinism God does everything but according to God's Word we have our part to play because it's part of a relationship, it's reciprocal

 Eternal security has been made available for the whosoevers but every whosoever has the choice to turn away from it if they choose to do so