1) We interpreted the 'triggering event' in the Gatling Laser rules as every instance a weapon generates a hit, e.g. if your al-Malik Moriah Cruiser scores four torpedo hits on my Grigori Cruiser then you roll nine dice vs these AD if your ship has three lasers. Since the gats are looking for sixes against torpedoes, this didn't seem harsh. Can you then apply the same lasers against the Moriah's next torpedo turret, its broadside of rockets, or indeed against any other ordnance-style weapon being fired into their arc? I know they respond separately vs grapple lines, fighters and boarding troops. This rule is not clear in the book but is critical for al-Malik players.
Yes. The gatling lasers fire against every attack.
2) It states very clearly in the rulebook that you cannot fire on one of your own ships at any time, but does that include when it is taken in a boarding action? Otherwise your opponent can from then on use a ship you can no longer fire upon.
Once they are captured they belong to the enemy. Shoot away.
3) Also on boarding actions, the rules state that a grappled ship can fire on the ship that is grappling it up to the point that the ships are drawn together. However some players then state that after that point, neither ship can be fired upon. If this is the case, then both ships simply sit in the middle of a battle while the boarding action takes place. Is this correct? In the 'Weird Situations' section of the rulebook it's acknowledged that the attacking ship could be rammed by an enemy ship during the action, so why not fired upon?
Both ships can be fired upon. There is nothing preventing it.
As I've seen them played, the boarding actions favour the Hazat rather heavily as they seem to get a lot of marauders as standard.
Yes, Hazat do get a lot of marauders. They do pay for them - their Galliot costs more. But other houses can buy marauders. And when the fleet book eventually arrives, it will offer rules for other types of troops.