In answer to the first that God is fair as man defines it Paul says God is "fair" in Romans 3:26. He is "just" and the definition of just is fair. Paul was using a common Greek term that the Roman Christians would understand, not some esoteric term that you had to have the secret decoder ring to decipher.
As to the second question "all have sinned and come short of the glory of God". "There is none righteous, no not one". "The wages of sin is death". That sums up man's natural state and is just and fair since all are held to the same standard.
Rom 3:26 To declare, [I say], at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.
This says nothing of "fairness" , it does not say that all men without exception are "offered this choice" It simply makes an affirmative statement that jesus justifies those that believe in Him
.And Who will do that
Jhn 6:44 No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day.
Jhn 6:65 And he said, Therefore said I unto you, that no man can come unto me, except it were given unto him of my Father.
Eph 1:4 According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love:
Eph 1:5 Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will
THAT is who will be justified by belief in Christ . I doubt you think that is fair
Soli Deo Gloria