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I’m concerned with the current wiring of a bedroom light switch box (4 gang, metal box with 4 on/off toggle switches).

Based on the Wiring Diagram included in the post:

1. I believe the ground wires need to be corrected. Please confirm if
   there is a problem with the ground wires. How should I correct if
   needed?
2. There is a giant wiring nut with 7 wires (6 black, 1 red)
   loaded into it… is this safe/up to code? What corrective action,
   if any, should be taken?
3. I want to remove the two left (shaded blue)
   switches. How should I do this and maintain electrical connection?