The characters are dressed in warm weather clothing and having an outdoor party even though the episode is set in mid-November (Veterans' Day) in Wisconsin.
If Red was in WWII and Korea, he would have had more than three diagonal, red longevity stripes on his sleeve. [EDIT]: In the US Army, each longevity stripe signifies three years of service. Red is a US Navy veteran. In the US Navy, each diagonal "hash mark" signifies four years of service. Three "hash marks" signify twelve years of service, making it possible for Red to have served during *both* wars.
When Red first gets the keg and Eric is pumping it up, it is floating in the tub, meaning it is obviously empty.
Red uses the word "wussy" in describing National Guardsmen as not being true veterans, but the word wasn't popularized until the early '80s.