What should I do about the king's illness? I was in the middle of a conversation with him...
And also, what kind of stats would my boat have, in case I decide to fight the slavers by Arborvent?
The king considered your words carefully and said that he might have work for you, but that you were to come back in three days' time and speak to him again. During that time, he was taken with illness. You are free to talk to the Regent though, or even to head to Altaregia by ship and throw your lot in with the Prince.
Basic transport capacity of 1 regiment and 1 str in a ship fight (but ship fights are added to by marine units or ranged units). Ship-to-ship combat might need reworking.
So, if you wanted to get into naval combat, hauling archers or marines onto the ship would work well. Or, of course, you could use your ship to ferry troops in the current crisis. You could technically blockade the port, at that.
I believe Osir is the only man with marine troops at present, mind. On the other hand, since there isn't a Royal Navy... you are in a unique strategic position regarding the civil war.
Edit: Regarding Trent raising a 'common' levy. That isn't a normal game mechanic. I decided that there was a secret mechanical benefit to his becoming a Trollslayer, which was attaining Popular Hero status. Tiakath might benefit similarly, but not in the exact same way. If a situation arises, it may spontaneously generate a benefit.