“If God does not rescue us from the furnace, we won’t bow?” What sense does that make? Of course they wouldn’t bow – they’ll be crispy critters!

The “If this be so” and “But if not” statements cannot be referring to God’s rescuing them or not. It has to be referring to Nebuchadnezzar’s threat of the furnace… ie.

“Nebby, if you go through with this, God is able to rescue us! But even if you don’t, we still won’t bow!”

There’s their faith and the reason for Nebby’s increased rage.

“Then Nebuchadnezzar was filled with fury, and the expression of his face was changed against Shadrach, Meshach, and Abednego. He ordered the furnace heated seven times more than it was usually heated.”