While I am not a proponent of the microniche concept, I have to ask, why are you doing it the hard way?
You don’t need ManageWP when most of those capabilities are already built into the basic WordPress script. You just need to configure it for multisite mode when you set it up. You can have all your micro-niche websites running from a single install. Download the free Windows Live Writer and along with WP configured for multisite, you have a much simpler and better solution that is totally free. You can run a thousand websites from a single WP script install.