I have explored everywhere I can. In the 2nd land I've explored all the areas I can without flying higher, including that cave though I can't go further in it since I keep passing out. The first land is also explored completely. I'll try again to see if I messed up my map though I don't think I did.
The Miasma Forest is a puzzle. To progress farther in it you need to take advantage of the various areas without poison. If you exit those places in the right order, and open up the shortcut from BOTH WAYS, you can progress.
I don't see how this miasma map is going to help me. I explored almost all of it, except for certain parts where the miasma is. Got nowhere. The guy specifically tells me to go talk to airships which can't even be found in caves.
There's a Mining Node in the upper left of the map (A2). You have to travel through the room with the Miasma to get there by taking various shortcuts and other exits since you're limited to 10 moves. --- Imagine I said something witty or profound here.
I don't know why you're so hung up on that, you were specifically told it's in the forest. You have to mine at the mining point in the Miasma Forest until you get the proper item, just like you did with the ore in the beginning. --- ~Mirror, mirror, on my floor, am I the prettiest at the store?