i found one way to defeat the king. Build LOTS and LOTS of ship of the line i mean REALLY LOTS. save, declare independance. see where the kings ships pop up. load. position your ships there. declare independance and try to whipe the ships out before they reach land. Somethimes a ship will get trough. so scramble almost ALL your forces to that point as well so you can try to defeat the landing forces. it worked for me untill i ran out of ships.
But i still think it is the only way. cause the ships will come in with 6 at a time but the troops with aroud 40 at a time.
What also helps is make a naval blokkade around the land so the kings forces can't land the first time. Or they have to attack you, but you will have the 10% defence bonus.
1 problem, you need lots of ships