Hi Ritchie,
Thanks for the detailed question. However we ask for debugging questions on http://answers.ros.org That’s a website optimized to get you your answers whereas discourse is focused on announcements and discussions.
Please reask your question there.
Having read your post, here are some tips to improve your question. Please check that you’re putting the turtlebot source in the src subfolder of your workspace. And be sure to build after you checkout the source. Also you don’t appear to be checking out the turtlebot_simulator repository which has the turtlebot_gazebo package. You may also want to look at the output of rospack list.
I’d also suggest that for getting the demo running you simply use the binary debian packages instead of trying to build it from source. You can just apt-get install ros-kinetic-turtlebot-simuator and the whole demo will be installed.