instead of just telling you it looks great I will try to help if I can.
You say all the vents were closed and it could not still get the temp to come down?
There is your problem. You should be able to extinguish your fire.
Thats the only way your Guru will work, it needs complete control of your airflow.
I would figure that out. Try an empty cooker and light some coals and see if you can get them to go out, maybe take the Guru off and try it.
Maybe a call to the maker of the pit is in order.
Ok Joe Offset, New Braunfels El Dorado, Weber OTS 22.5 & 18.5, (2) Master Forge Charcoal, Auber ATC, charcoal retort Weber drum rotisserie