To save the last edited timestamp and user I suggest modifying the ini structure a bit. Namely you might want to consider losing the Define-Explain key in favor of the actual word. This does, however, set some rules to the definable words. For example the words can't have a "=" in them, since that's a crucial character of .ini file format.

Anyway, writing could go as:
/writeini Worddata.ini $2 definition $3-
/writeini Worddata.ini $2 user $nick
/writeini Worddata.ini $2 timestamp $timestamp

And reading:
if ($readini(Worddata.ini,$2,definition)) {
.msg $chan $2 == $v1 set by $readini(Worddata.ini,$2,user) at $readini(Worddata.ini,$2,timestamp)
}
else {
.msg $chan $2 == Not Yet Set.
}