Calibrated means I checked the temperature with an IR or thermocouple thermometer. The meter on the front of a typical hot air SMT desoldering contraption measure the handpiece temperature, not the work temperature, which is affected by the distance between the handpiece and the work. The front panel display is only a good starting point.
I don't apply heat full blast when starting. I wave the handpiece around a little at a distance to get things warmed up, and then hit with maximum heat. I'm more worried about melting plastic parts on the PCB than about thermal shock.
The rubber ESD mat must smell really bad. Heating my formica top plywood and steel frame workbench would be a real challenge. I assume you use an electric heater as building a wood fire under the workbench might be some kind of safety violation.
I have one of these: It think I paid about $80 about 5 years ago. If you compare the various hot air machines, you'll probably notice that the handpieces are almost identical. It's the handpiece that makes the heat. All the goodies in the main box do is regulate the temperature and fan speed. Unless you need precision control over either of these, all the various boxes are functionally identical.