For my addons, I don't worry about the keywords or the changelog. I just enter in commit notes however I please and then copy/paste them into the changelog field for the download page. I don't use the externals feature, either (used to on the old wowace svn, but not since they moved to Curse), and I just hard embed the libraries with my addons (ie, including Ace3 when commiting to the svn). What you wish to accomplish can be done, I just either haven't done it in a while or aren't sure how.
As for your dependency question, however. You don't include it with your addon for download. You merely link to it and state that it is a dependency for your addon, and that folks need it.