God Repents Of Evil In Jonah 3:10

Here's some food for thought on the NIV translation of a confusing verse (and here the NIV seems in common with most other modern translations) (and -duh- all emphasis mine):

Jonah 3:10: "When God saw what they did and how they turned from their evil [rah] ways, he had compassion and did not bring upon them the destruction [rah] he had threatened. (NIV)"

And in the RSV: "When God saw what they did, how they turned from their evil way, God repented of the evil which he had said he would do to them; and he did not do it." The KJV is identical in relevant parts.

My thoughts are simple and predictable.

1) I am puzzled beyond words at this notion that God would repent of an evil that He had intended to perform. Now, this doesn't concern me, as I take "evil" here to mean something like calamity, injury, misery or distress (all part of Strong's definition). What's puzzling is that God repented of an act He had willed to perform. What of God's being without passions and "immutable" (WCOF, Ch. 2, I)? Of course, if we white-wash God's intentions down to a mere threatening, we have cured any conflict between Scripture and a certain confessional tradition.

2) What gives an editorial board or "translation" committee the power or authority to decide that the same word should be translated two different ways in the same verse? This, as a license, makes me tremendously uncomfortable, especially under the rubric of an all-sufficient and entirely perspicuous view of Bible. Let evil be evil, and let God repent away, if that is what the Spirit-breathed words tell us.