1) if the user's account name doesn't correlate with the drop-down choice, I'd like an alert to appear to make the user either select the correct name, or re-login.
Use OnObjectValidate to perform a script. The script can use the value in the field and Get ( accountName ) (identify individual) or Get ( accountPrivilegeSetName ) (Identify user as member of a group) to determine whether the current log in is appropriate for the value selected.
2) you haven't really spelled out how records with "complete" and "incomplete" status should be handled so I can only list possible approaches:
OnRecordCommit can be used in a fashion similar to OnObjectValidate to check for completeness.
Conditional formatting on required fields can highlight the fields in a contrasting color until they contain data
A calculation field can return the text "complete" or "Incomplete" based on what fields contain or do not contain data.
Layout text can be set to be invisible if the record is "Complete" and visible if it is "Incomplete" or vice versa.
Navigation buttons on the layout can perform scripts that refuse to take the user to another layout or record if the current record is not complete.