Just curious, if you have a ship that has Swarm Tactics and its killed before it activates to shoot, does a ship at range one still fire according to the pilot skill it would have received from the other ship (the one with Swarm Tactics) or does it revert to its default pilot skill. I assume the first interpretation is correct?

Secondly, am I correct in assuming you can string Swarm Tactics. Example, Pilot Skill 9 gives it to pilot skill 7 and he in turn gives to pilot skill 2 (assuming they are within range 1 of each other). In this case 7 becomes a nine, but does the last ship get a 9 or a 7 as its rating?

you can string swarm tactics. Swarm tactics is activated at the start of the combat phase, before any ship has fired a single shot. If your ship that has given another ship swarm tactics kicks the bucket, that other ship still benefits from the swarm tactics until the end of this turn

and thru the stringing of warm tactics, does that make all the ships the highest pilot skill, or just the same as the ship that granted it swarm tactics?

All the highest. Vader (swarm tactics) > howlrunner (swarm tactics) > any other ship means all are now firing first at skill 9. Otherwise it wouldn't be chaining, just using it twice.