You should work a bit with that sea background. It looks bad because of the amount of repetition. Unfortunately, it isn't as easy to cover up as land, but you should at least be able to increase the scaling a fair bit to at least lessen the effect.

Since this is a close-up map, I would also have looked into adding more depth contours. A detail map of a region will usually have smaller interval between contours than the main map, thereby exposing additional contours that's not visible on the main map. The smaller scale also makes it reasonable to add areas that was too small to include in the overview map. I think I might actually see some indication around the Islands when I look close, but it is a bit too small and subtle.

I have to agree with Sue, making them inside CC3+ gives the best results.

The important thing to keep in mind when you try to use intermediate formats like .dxf/.dwg is that dxf/.dwg may not support all the features from Inkscape, and CC3+ may not support all the features from that dxf file again, resulting in a file that will probably be severely lacking compared to the original in Inkscape. Working with vectors isn't like working with images, where it will look identical whether you save it in .bmp, .jpg, .png or .gif, on the contrary, it's probably going to look quite different. Basic shape will be usually preserved, but all the more fancy stuff are likely to not survive the conversion. (Think of it as saving a fancy word document to plain text. Word supports it, but it looses all formatting like fonts, colors and lots more.)

This will happen if the fill isn't defined in the map, such as if you are using an existing map made before this fill was added, in which case you must import the fill into the map first. See this FAQ entry:

Looks like the entity is simply too complicated here because of too much fractalization of the walls. The existing entity has 32632 nodes. That's bordeline what the tools can handle.

I recommend you reduce the node count of your entity somewhat. Try using the SIMPLIFY command on it (I suggest trying with a simplification distance of 0.1), this should reduce the node count significantly.

For your particular map there, you'll also need to consider how to handle "holes", (i.e. solid walls in the middle of the map). A standard CC3+ polygon cannot have holes in it, which you seemed to have noticed by the area up near that entrance to 10 not being closed properly. This is something you probably should consider right now before doing any more work.

There are three ways to handle holes. The one is through the use of a multipoly, where you draw the base floor only following the outer outline, and then you draw the inner walls as their own polygons and merge everything together using a multipoly. This works, but the multipoly cannot be edited by the drawing tool edit command once joined (without splitting it up again, then editing, and then joining it back together), so this approach works best if you plan for this and do the actual outline first.

The second way is basically draw the inner walls as their own polygons on top of the floor, usin an appropriate filling for the walls, and just accepting that the floor doesn't have holes where these walls are, but instead a wall covering that part of the floor.

The third way is through the use of the color key sheet effect. As with the other options, the main floor needs to follow the outer outline of the floor, and then all the inner walls are drawn in a distinct solid color on the same sheet as the floor, and the effect is used to "knock out" those parts, creating the visual appearance of holes.

You can use the macro commands GOLAYER and GOSHEET (or LAYER and SSET if you prefer an error message instead of creating a new layer/sheet if it doesn't exist)

Using them by themselves may not speed up things too much since you need to specify the name, but you can then define your own named macros using something short and easy to go to a predefined sheet directly. And if you want the same command to just go to the next in a list, you should be able to set that up by using a variable to keep track of state and then using a conditional to activate the next sheet.

You can also add your macro commands to the CC3+ menus. This allows you to easily activate it from a menu, but maybe of equal interest, you can add shortcut keys to any menu command. Read more about menu editing.

Lastly, you can also use the SNEXT/SPREV to go to the next/previous sheet in the list. (There's no equivalent for layers)