Vent on top should be open all the way. Either weber lid or bung hole. Then only use 1 ball valve to adjust the air coming in. The othere 3 valves are mostly for bring the UDS up to temp. Then close them and only use the one valve.
I added a clay pot diffusser to my UDS. That seemed to help me with the see-saw temp changes.
22.5 WSM, 120 Gallon Offset, Weber Performer, IQ-110, ET-732