Randi - excellent observations!!

First off - "Than" is used as a comparative statement - comparing this to that. (example: I am older than you!) "Then" usually refers to a time or sequence (example: "Then" we went to the store.)


I am afraid that "could of" is just slopping speaking which gets translated into sloppy typing. It should always be "could have!" You are one that certainly puts us English speakers to shame.