Uh, in the file you posted there is nothing on the WALLS 2 sheet, not is there a point light, setup on that sheet.

I've attached a version of your file where I threw in some crude light blockers on this sheet, to prevent the outside light from illuminating the walls. I placed them a bit from the edge to show the edge of the wall, but they block the light from getting far into the wall.

Also note you should put your bitmaps in the final resting place before using them in a map. The paths for many of your fills refer to your download directory. The next time you clean up your download directory and moves the files to a better locations, those ice fills will suddently start showing red X'es.

That's a "Whole Drawing" effect. You can switch to those using the radio buttons right above the effects list in the sheets and effects dialog.

Yes, the important things is the images on disk, not the symbol themselves inside CC3+.

This dialog is shown if there are no catalogs matching the current filters (which depends on map style) or if there are multiple catalogs. If it is normal behavior or not really depends on the style of your current map. For example if you start a city map, and then switches to the Dungeon Designer toolbar and click the button, it is normal behaviour, because there are no wall feature catalog for city maps. On the other hand, if you are using a standard dungeon map like the SS4 Mike Schley or DD3 Dungeon style, you certainly shouldn't get an empty list here. But again, it depends on the type and style of your current map.

Certainly not if you are doing a dungeon map, as that is a city filter (The CD at the beginning stands for City Designer). Thjat should only be the active master filter if you are working with a city map in the CD3 bitmap A style

Your map should normally load the correct toolbars and master filters every time you open the map, so you shouldn't need to mess around with these values.

Those lines you see are a selection. You didn't say which tutorial in the tome you followed, but since you are getting selection lines, I am guessing the one on page 717. If so, you are getting exactly what you should. That tutorial is for loading a selection matching the shapes of your continent, and then you can use FT3 commands on that selection, for example raise land and such. Once you use those commands, you should see actual land forming inside that selection, giving you your landmass.

Your map is a pretty poor selection mask though, as the sidebar by that tutorial explains, white is used to determine inland areas, black is sea. So right now, your map depicts a planet that is basically just land, except for a few very thin river-sized lines of sea.