I am also American, but would agree with the usage of "in" and "on" in each of your four examples. "In" has the connotation of examining or studying the contents of the list, maybe even how the individual items relate to one another. "On" seems to be concerned with only whether or not something exists on said list. "Hey, am I on the list." "Did you put that on the list?"
"On" in number four is tied to the expression "list of priorities," and I have only ever heard it expressed "on my/her/his list of priorities.