Since then we are delivered from our misery solely by grace through Christ, without any merit of ours, why must we still do good works?
Because Christ, having redeemed and delivered us by His blood, also renews us by His Holy Spirit after His own image, that so we may testify by the whole of our conduct our gratitude to God for His blessings, and that He may be praised by us; also, that everyone may be assured in himself of his faith by the fruits of it, and that by our godly conduct others may be gained to Christ.
Can those who continue in wicked and ungrateful lives without turning to God be saved?
By no means, for the Holy Scripture declares that no sexually immoral person, idolater, adulterer, thief, greedy man, drunkard, slanderer, robber, or any such like, shall inherit the kingdom of God.