Have to ask, there are Troops actually aboard said ship?

Asking from experience...

2 - How do you see the details of ground units embarked in TT module? I would like to add a 100-tons TT module on each of my medium+ warships, but it seems you don't know much about the troop once it is boarded.

You can see some information in the "Transported Items" tab on the naval organization window. You can also see the entire formation detail on the Ground Forces window, OOB tab, if you check the box to show units on ships (which is off by default).

As an aside, while 100 tons is probably fine for ship's defense squads, I would probably suggest using 200 tons if you want to conduct boarding actions, as I've found in practice that 100 tons is a bit too small for most typical ship sizes you might want to capture.

STO's workwith theweapon you built for them. So if you want them to use spinal mounts, then you need to design a spinal laser/plasma cannon and put it in an STOmount. I and at least some NPR's do this so it is straightforward

I had setup the Truce countdown for 20 years, and 4 years after my start 2 of the NPRs in Sol (Greater China and Southern Federation) are exchanging blows. The DB is showing 0 for the truce countdown, so somehow it has been set to 0 for reason unknown.

I highly prioritize fuel efficiency. Heck, my newest generation of fighters can go nearly 10 billion km (up from 8 last generation).

Also, due to the quirks of my galaxy layout, it's at least a 10 billion km trip from Sol (where my shipyards are) to anywhere else. I want to move the 'yards somewhere more centrally located, but the crazy manpower requirements have stalled progress on that front until I can build up population in the colonies.

My explorer ships have deployment times of 3 years, and maintenance stores to match - they're as fire-and-forget as I can make them. Admittedly, 810 billion range is probably more than I need (they usually time out or start running low on supplies first); but they're only running with 750,000-size fuel tanks - the efficiency of 5,000 ton engines with 30% fuel efficiency and 50% power stack to a crazy degree.

My survey ships have ~100b range and my warships ~20-30b, what is wrong with you people?? 

It's the best way to make explorer-class vessels. They need to be military, but you don't want them running out of fuel.

My current generation of Exploration Ships has ten times the range of my (similarly sized) Destroyers (810 billion km vs. 80 billion km) with the same fuel tank.