Plenteous Redemption

Why was David crying unto the LORD? What are the 'depths' that David is going through? Why does affliction cause 'soul searching' and for what does God purpose these afflictions for? What does mercy mean? What do sinners deserve? Why is the LORD merciful? Who is the ransom? Is there a need to be redeemed? Is this need for those of yesteryear? How does sin effect the redeemed? Why did Saul chase and persecute David? Who is the Glory that shall be revealed in His chosen ones? Who are the 'sons of God'? What is the only way a man can look upon the Holy God? Can any man glorify God even in his best state? Is there any limit to God's mercy and power to save?