I don't have a triple, but I can't see how it could be a problem. You clamp it to the frame so that the working part of the blade is about level with the teeth on your small ring.

definitely will reach the small cahin ring, I used it on my tandem with a triple chain ring and there is plenty of adjustment.

Yes it should do if you have straight tubes, i.e. an aluminium or steel frame. If you have a carbon frame with a seat tube that flares out towards the BB you might not be able to mount the K-Edge low enough. I reckon you need about 35mm of straight tube below the front derailleur band for the clamp to fit for a triple although at this level the bottom bottle cage mount might hinder you. On my compact double the K-Edge clamped straight between the derailleur band and the bottom bottle cage bolt.

I used the same as recommended for my front mech: 5nm. Seemed logical and safe.

Refer to the manufacturers instructions of your frame. If it's carbon fibre then light as a feather!

I'd recommend the carbon friendly gloop you can get that adds grip and means you don't need to tighten so much. I use it for my seattube too...

Take a ruler and measure the diameter of your seat tube.

I used it on a triple chainset on my tandem with no problems.I have the Ultegra deralier and used the clamp on system

It measures about 77mm from the top of the clamp to the bottom of the blade, and the working part of the blade is around 30mm long. I don't know what a moda stretto is, but I have no problem with SRAM Red on a monocoque carbon frame.