Yes, the tempo is in Bpm. You can control it with the curve or the value inlet on the top left corner.
Simply drag and drop an Device’s address or connect a cable to it.
If you want to change the value with a trigger and you found the speed parameter in the local device, the easiest way would be to drag and drop the speed parameter in question with value onto a state (dot at the begging or end of an interval).
you can then add a trigger in the same place and you will send the single value 0 to speed every time it is triggered. Same thing with 1 to start it again.
Does this make sens to you ?
It should work in theory but you may encounter an issue specific to sound files.