I have on of Wang's 12V DC fan. The Wang fan has a huge CFM output and will likely be able to handle a small commercial size smoker. The UDS is a home size smoke that would be an XX-small commercial size. All DC fans have a min. starting voltage needed. The 60% is likely too low to start your particular fan. You'll likely to get better results with a with a higher min. voltage (>60% setting). You may need to limit the amount of air blown to the UDS by adding a restrictor (something to partially block the air flow) or an air bypass (add a Tee fitting between the fan and smoker). Other brands of controllers have smaller output fans (lower CFM and run at near full CFM output, that is run at the higher settings.
I know of no smoker controller has used the PWM to control the fan speed. This would solve the stall and fail to start issues. The fan that Wang sold has 4 wires -- 2 wires for the DC postive and negative, a tach wire and a PWM speed controller wire. Much more expensive than the typical 2 wire computer fans. Using a Goolgle search, PWM controllers for temp. control are expensive, except when used for computer fan controllers. Unfortunately I don't know how to re-engineer one for the Q.