We disagree about the meaning of I Corinthians 3. I do not believe any of us are lifting grace above Jesus. It is through Jesus that we have the grace of God. Without the Lord Jesus, we would have no grace.
No, sin does not only lose Earthly rewards, but Heavenly ones as well. But sin does not take away your salvation. There are many verses about the saving power of Christ.
Ephesians 4:30-32 "And grieve not the Holy Spirit of God, whereby ye are SEALED unto the day of redemption. Let all bitterness, and wrath, and anger, and clamour, and evil speaking be put away from you, with all malice; And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you."
Saved people can grieve the Holy Spirit, and do all these things, but the person is still saved.
II Timothy 1: 7-14 "For God hath not given us the spirit of FEAR; but of power, and of love, and of a sound mind. Be not therefore ashamed of the testimony of our Lord, nor of me his prisoner: but be thou partaker of the afflictions of the gospel according to the power of God;
Who hath saved us, and called us with and holy calling, NOT ACCORDING TO OUR WORKS, BUT ACCORDING TO HIS PURPOSE AND GRACE, which was given us in Christ Jesus before the world began.
But is now made manifest by the appearing of our Saviour Jesus Christ, who HATH ABOLISHED DEATH, and hath brought life and IMMORTALITY to light through the gospel:
Whereunto I am appointed a preacher, and an apostle, and a teacher of the Gentiles.
For the cause which I also suffer these things: nevertheless I am not ashamed: for I know whom I have believed, and am persuaded that HE IS ABLE TO KEEP that which I have committed to Him against that day. (notice that Christ is doing the keeping, not Paul- also note that Paul says he knows who he has believed, not what he has done to keep his salvation).
Hold fast the form of sound words, which thou hast heard of me, in faith and love which is in Christ Jesus.
That good thing which was committed unto thee KEEP BY THE HOLY SPIRIT which dwelleth in us.
How are greedy people punished on Earth? Idolaters? I don't know. I would suppose the chastisement is different for different children. One thing I do know is that being out of fellowship with God, that chasm between is a judgment in itself. David speaks of this when he cries out to the Lord, "Restore unto me the joy of my salvation."
Jesus says in John 10 "But ye believe not, because ye are not of my sheep, as I said unto you. My sheep hear my voice, and I know them, and they follow me: And I give unto them ETERNAL life; and they shall NEVER PERISH, neither shall ANY MAN PLUCK THEM OUT OF MY HAND.
My Father, which gave them me, is GREATER THAN ALL; and NO MAN IS ABLE TO PLUCK THEM OUT OF MY FATHER'S HAND.
I and my Father are one."
Capitalization is for emphasis, not for shouting.