If a moderator holds a question, does s/he get notified when I edit the question to address the hold? Or do I need to comment in reply to the moderator that I've changed the question?
As far as I know there is no notification made to any user when a question is edited.
The only thing the edit of an On Hold question does is to place it in the Re-Open queue for reviewers to assess whether the edit has been sufficient.
I think questions in the Re-Open queue are presented to non-Moderators first because there appears to be a lag before I see them.
An @reply in a comment is the best way to notify a Moderator that you have edited a question that they have placed On Hold.
The other way is via a flag, but please try using an @reply first because that way only the specific Moderator who placed it On Hold needs to re-review it.