When you outline a multipoly, the outline itself also becomes a multipoly. Amultipoly is always a filled entity, so you cannot set line width on it. That thin outline you initially get is the Hollow fill style, which is the only way to have an outline with a multipoly.

However, the main reason for having a multipoly in the first place is so you can have a hole in the poly. For the outline, this is kind of irrelevant because it isn't a solid surface you need a hole in. So you can explode the outline you get, and then use change properties on it (remember to pick all the entities that made up the outline multipoly), and set the fill style to solid, color to black, and a line width of your choice.

That scale does sound a bit weird when I look at the symbols on your map. Even the tiniest buildings I can find in your latest map would then be about 50'x50' and the trees fill almost an entire 200x200 square on their own.

You're using a symbol fill, right? You have to edit the actual symbol used for the fill. Open up Symbol Manager, and check the "Show Fill style symbols" option. Now you should be able to find the symbol in the list, and you can edit it from there.

If you don't find the correct line style, it is easy enough to make your own. Just click the line style indicator, and make a new style. For a dotted style, you'll want very short line segments, and a distance between them that is still quite short, but at least twice as long as the line segments. And make sure you don't use paper scale.

Yea, as I mentioned above, you cannot edit a multipoly properly, which is why this should be the last thing you do.

To edit the multipoly, you need to temporarily disable it.

1. Hide your walls to avoid accidentally messing with them.
2. Use :CC2EXPLODE: on the floor entity. You'll notice that your "hole" disappears, but that piece of floor we used to make the hole in the first place should still be there, although it may be difficult to see.
3. Show the walls again.
4. Do your edits. (Note that we did move your walls to other layers/sheets, so make sure the oultine entity of your drawing tool is updated with the same changes, or it might not work properly)
5. Hide the walls
6. Use :CC2MPOLY2: again to combine the floor with the hole.
7. Show the walls.