What determines where I should set the autobrake?
Runway available and all of the factors which affect stopping distance required.
In this case, what were the field conditions? From the visuals, I'm not confident that the runway (8994') is dry. Brakes 1, which you have set, produces very long landing rolls. So long, in fact, that we are not allowed to use it. Brakes 2 is the minimum. 8994' at that field elevation is not a long runway. Unless it is dry, and you're pretty light, I'd go with Brakes 3. If braking action is less than Good I'd go with Max.