We do not know what event sparks the start of the war. The first aggressive action by Kooluk against the Island Nations is the attack on Razril after Lazlo acquires the RoP from Glenn (Cray has the Kooluk fleet attack Razril because he knows someone in the Gaien Knights got the RoP from Brandeau and he thinks it is still there). There is no mention of any open hostilities with Kooluk before that point in the game (just that Kooluk is Gaien's enemy nation and that Glenn had fought with Troy 7 years ago).
It is mentioned in one of the book volumes that Gaien made the first move against Kooluk because they knew about Fort El Eal being built on the shores of Kooluk and saw that as a threat (the start of Kooluk's expansion overseas), so Glenn lead the naval force against Kooluk and was repelled by Troy. This might cause some confusion with when the war actually started because we don't encounter any Kooluks in the game until after we get banished from Razril and the war between Kooluk and the Island Nations officially kicks off when Kooluk finish their giant rune cannon and use it to zap Illuya.
Rikie says that her husband got the RoP "three years ago." That places it sometime between Year 299 and Year 304, depending on how early in the war she is recruited. This happens very early in the game, so I am assuming it is either in Year 302 or 303. Rikie says that her husband was at sea when he got the RoP, so it is unlikely he was present when Cray's village was destroyed. Why would a Na-Nal fisherman be so far inland in another country? So he probably did not get the RoP from Cray's son. It is unknown how many people were in between these two bearers. Rakgi's father probably inherited the RoP around the Year 300.
We don't know every single person who ever held the ROP (after all, Lazlo never had any visions of Steele, he only ever seems to see people he knew personally or relatives of people he meets)
As far as I can see...
Queen of Obel has ROP first. Lino says this is 15 years before we destroy El Eal.
Queen of Obel dies and the ROP passes on to an unknown person (a surviving pirate or soldier perhaps)
The ROP continues it's journey from host to host and makes it as far as the borders of Scarlet Moon, where Cray and his son encounter it.
After Cray's mutilation and the death of son, it passes on to another unknown person/s and eventually ends up back in the Island Nations.
Then Rikie's husband got the ROP. Perhaps he found the rune bearer lost at sea or washed up on a beach and it passed onto him.
Then Steele posseses it. I think it is possible that Steele attacked Rikie's husband's fishing boat and Rikie's husband was killed in the attack and the ROP passed onto Steele.
Then we know that Steele is defeated by Brandeau and Edgar, and that the ROP passes on to Brandeau. And we know what happens from there.
Personally I'm more concerned about the order of events, not too bothered about the year numbers.