Uninstall Mac OSX Server while inside the OS installer

I have a bit of a problem. I recently undusted my old Mac Mini 2011 I received as a gift a couple years ago. It was running Mac OSX Lion on a Raid 1 setup with two 500 GB disks, with an older version of Server. It had the Sierra installer already downloaded to it so I ran that, only to be told that the installer is faulty and to reboot. After rebooting I found myself in the installer again, this time prompting to redownload Sierra. It did and attempted to install, then said there was an error and rebooted. Upon rebooting, it told me that Mac OS Sierra is not compatible with the version of Mac OSX Server, then prompted me to reboot again. I went into recovery mode and am now trying to re-install Lion, which takes a while because my internet is slow. My question is: Is there a way to completely uninstall Mac OSX Server through the Terminal app the installer provides? Is there a good chance Sierra installation will just work once the Server app is gone? I remember being told to update the Server app the first time I tried installing Sierra. But since it let me continue, I figured the Server app would just not work or get deleted during the installation, not brick the system installation. Edit: Screenshot of failed Sierra Installation