There are Vahnatai all through this level, and all I've tried to do is show the major groupings. You'll also sometimes find them in the side rooms, and they'll randomly sneak up behind you as you go through the level.
If you have Erika's Amulet you have two choices for how to get through this level. If you have the amulet it will send a bolt through the walls clearing a passage from where you entered in Footracer Province to where the level exits into the Vahnatai Lands.
The other way is to make your way through. I try to consider the three levels as three seperate dungeons, not moving onto the next until I've cleared the first.
Use the map to see the locations of secret passages and battles other than the Vahnatai. A couple important items of note though. The room containing the two crystals on the north side of the second level both have effects. The eastern crystal will give you one point in Magery, and the western crystal will drain your experience. The second thing of note is the Wretched Demon. These are very hard. I had just leveled up to level 79 on the level above the Wretched Demon, and I levelled up again when I killed it. That should give you an indication of how tough it is by the amount of experience received for killing it.
The boats in the northeast corner don't seem to serve a purpose, since you can reach everywhere they take you without them. I think they're meant to be a shortcut from the third level to the second level, but I'm not sure.