I have no idea for 1 and 2, but some triggers (some Roland triggers, for instance) are too "hot" for the Dm10 module, causing electronic crosstalk - other neighboring triggers are triggered by the voltage. A resistor (80kOhm, for example) takes care of that.
When I had the "too hot" trigger, I could max out the volume meter in the Ext Trigger menu with a low sensitivity of 10 or so. Rule of thumb: if you can max out the volume meter with a sensitivity of 12-13 or so, the trigger may be too hot - add a resistor.
The hi-hat input handles about 3-90kOhm or so - just connect it to a 0-100kOhm potentiometer and try the calibrate routine. The stock pedal is about 0-70kOhm. The module can't distinguish between 0 and about 2-3 kOhm, so you could just as well add an extra 2kOhm to the pedal cable and get a tiny bit extra out of the pedal sensor.
It doesn't matter if the pedal outputs 0-20kOhm or 0-80kOhm - the module will adjust. I tried boosting the output of the Roland VH-11 controller - made and added a powered circuit that trebled the resistance output of the pedal - no effect.
