You will need to complete the game to unlock all the maps. I have pretty much done everything, so I would be more than happy to walk people through the game at what ever level you happen to be at.
I do not recommend a complete ghost ship run as that takes too long, like an hour+ a run. But a run to the true objective is time efficient and quite rewarding. I will not be a ghost ship run for anybody who is not level 45ish. You either go for the true objective or go home. People of lower levels will not make it through.
The problem your having on the ghost ship Halberd is that you were under leveled. Attacking higher level enemies does reduced damaged. In the other thread I recommended a minimum of level 45. Not to mention at the time your equipment is all out of whack.
We going to use IRC for this? FC: 3222 5727 4873. Remember to PM so I can counter code. As an additional note, lag shouldn't be much of an issue, it's surprisingly tolerant because of the game design, but if your lower level than I, I suggest you host so you can have host advantage.
I also suggest you go to
Halberd's guide thread, although not exactly for the guide itself as most of the information pertained within it is inaccurate as it does not reflect online realities. However the thread itself contains a lot of solid advice and I am available to answer questions there.