Add a Mossburg 500 pump gun, 200 rounds of 3”#2 to your list.
Got it, but only have around half the rounds. Difficult to procure.
2-3/4 inch shells in 12 gauge are more than adequate. 3 inch shells can cause injuries at both ends of the gun. Plus they reduce capacity.
Good choice for the shotgun. Mossberg 500 or Maverick 88 with the 7 round magazine.