To address the 5th point of your steps, just use the mail utility if you have it installed on your system. Check its man page for detail.
As far as the 8th point, I would approach it in the...
As a start, this will filter out all accounts that didn't log in the last 41 days.
Bear in mind, that this will also list technical user, for example for daemons, as they never logged in, most...
There is no /etc/shadow on AIX. A similar file is /etc/security/passwd and some others in that directory. The information you are looking for should be in /etc/security/lastlog.