Has anyone built a custom solution where the content is updated/changed in your own software/database and then pushes those updates, content changes to Moodle site?
Yes, we are doing it, although the plugin we use isn't public so the fact that we do might not be very helpful to you.
Our content creators use an in-house XML format that we call "Structured Content", which is usually authored with the Oxygen XML editor an published to Moodle using a custom plugin we've developed. (We do this largely so that it can be readily converted in to other formats for users who want something other than a web page).
Thanks Mark, very appreciated for your reply. I am continuing my search for something that will fit our needs, but more and more each day, it seems that a in-house custom solution may be the answer. Which is what your institution has accomplished.