On the first two: check to see if there is a "/Users/jsn Deleted" folder, that will contain all of your old files. If there is no such folder (or no similar folder) then you're up the creek.
Rule #1: Always keep backups
Rule #2: Always make a backup if you're going to mess with anything serious on your system, like your user account or do a major system update.
On the third, Apple Menu -> System Preferences -> Users -> Users Tab: select your account and check the "Login user jsn automatically" checbox at the bottom of the page.