mm wrote:

1) The machine has a device to turn the dryer off when the clothes are
the desired dryness. You point the dryness knob to the chosen dryness
and turn on the dryer. But then the knob rotates and the pointer
moves. How does the dryer know where I set it?

With the "auto dry" feature, the timer advances in relation to the
demand for heat. The heater has two levels -- on and off. When the
dryer starts, the heater is on until the exhaust reaches a predetermined
temperature, then the heat stays off until the exhaust reaches a cool
point and the cycle repeats. The timer advances only when there's no
demand for heat. With a wet load, heat is lost in the moisture, so more
heat is necessary. As it drys, there is less opportunity for heat loss.

...But the air with this machine, even on gentle, must be a lot hotter
than gentle. Even after I've opened the machine and taken out the
clothes for a few seconds, the clothes seem hotter than gentle. I'm
afraid to try the next temp up...

Is this different from what you experienced before? If the dryer has a
switch to select between two or more heat levels, is could be stuck at
the hot setting. In some dryers the low setting is determined with a
resistor near the thermostat that warms up to "fool" the thermostat into
opening (shutting off heat) at a lower temperature.