Map editing: List of unused tilemaps?

Hello all,

just a few quick questions about map editing with FF6LE-CE as I'm currently in the middle of drawing some additional maps:

1) Is there a list of tilemaps which are unused in the vanilla game somewhere around? I couldn't find one on the forums, so I did a quick look through all maps in the editor and came up with the following:

Tilemaps 2C, A8, A9, F5, 12A, 12D, 12E, 15E, 15F didn't show up, so is it safe to assume that these are indeed unused and thus available for custom maps?

2) What is the upper limit of different tilemaps in the game? The ones listed above will likely not be sufficient for my project, so I'm looking for ways to get additional tilemaps available. The highest tilemap number in the editor is 15E, and 15F seems to work okay, too, but going higher than that led to an issue of not saving the map correctly. I tried tilemaps 160 for Layer 1 and 161 for Layer 2, but after 4 hours of map drawing and saving, I had to find that my new map was gone after reopening the editor. I never got a warning message when increasing the tilemap numbers, nor while drawing my huge map. I doubt that I exceeded the available space, as this would normally produce the warning message informing you that it didn't save, so I'm not sure what's going on.

3) Can a tilemap only be assigned to one Layer, or can it be used for two or three layers as well? Like, if a certain tilemap number is currently used for Layer 1, it only contains the Layer 1 tiles of that map, right? So could that same tilemap number be used in a different map for Layer 2, containing only Layer 2 tiles this time? Or is any tilemap number restricted to use of a single layer? (oh man, I hope you understand that question, lol)

Thanks for any help you can give me.