"1. Can point defence cannons shoot down energy-based missiles/torpedoes?"
Yes
"2. What is the difference between meson and anti-photon bLasters? All I see in the descriptions is slightly varying amounts of damage. ..."
Keep watching. Meson is in the end cheaper to research, and 10 KT smaller, and it's damage does NOT vary with range. APB gets out to range 8 with higher starting damage, higher research cost, and a damage dropoff.
"3. A massive shield depleter is showing up as doing only "1K" damage. Is that a misprint of some kind? Also the fire rate is showing as 30, as in thirty. That can't be right."
1k. Correct.. one THOUSAND points of damage. Look a little better now?
30 is correct. Like the rocket pods, one-shot weapons.
"4. If stealth armour is described as "only one component per ship effective" does that mean there's no pint adding more than one of them? Same for the other armours or do they stack?"
The armor effect stacks; the 15% ECM bonus does not.
"5. What is the difference between fleet and ship training? That is, is there any reason not to build fleet training facilities only and keep all ships in a fleet, even if it's a fleet of one?"
They stack. Ship+fleet = total bonus
"6. How does multiplex tracking work exactly? I watched some of my ships in action and it appeared that they didn't attack a second target after the first was destroyed even though they had weapons that had not fired yet. "
Multiplex is.. odd.
Phoenix-D