Edited: another fuel/temp gauge thread, but turns out the harness is melted together

I will pull the cluster and check all of those connections.

Would a missing/disconnected fuel tank ground strap cause these readings?

How do I test whether the correct amount of power is reaching the gauge cluster?

I understand that the cluster is powered by G5 which is a dark blue wire that connects to the printed circuit board and powers the gauges and warning lights:

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