There are lots of ways to do this with sheet effects. This is just one of them.

You could add a Color Key sheet effect to the sheet you have your 'floor' level on and draw a magenta polygon (Colour 6) where you want the crack, then add a narrow Bevel, Lighted effect. You would have to uncheck the global sun direction in that effect and adjust the azimuth angle to be opposite the global sun azimuth (that usually means making it 135 instead of 315 degrees), but that should give you a crevice.

Then you would need to add a new sheet for your flooded level under that floor level so there is something to be seen through the hole you just ripped in the floor.

The reason the bevel would have to be narrow is to make it possible to hide the outside edges of that floor either beyond the extent of the map or under a wall. The bevel will be applied all around the edges, including the outside edge.

Ok. I think it's coming along pretty well. The main thing I would adjust if I was using it myself for a map is the hills. I would use effects and settings similar to those found in SS5, though I adjust those to make the bevel lighter again than it is in the template.

The HILL sheet uses polygons of "Solid 20", and my personal settings for the Bevel, Lighted sheet effect give the hill a highlight as well as a shadow. It's personal taste, of course, but I find the template setup makes the hills a little too dark for my liking.

These settings also use a lot more smoothing than you have in your template. It gets rid of the knife edge ridge which feels a bit unnatural for a relatively small hill - unless they are meant to be mountains.

Having sufficient edge fade on the hill after the bevel also helps to make the hill look like it's a rise in the ground, rather than something stuck down on top of it - a curve into the slope rather than a sharp line, or a line that hasn't been faded enough with a wide enough EFI. I increase mine from 10ft to 15ft, though it could be wider.

You could try switching them off on a sheet by sheet level by unchecking the little box next to the effect - if you really need some of the effects but not all of them to be able to see what you are doing.

It looks like the low res versions of the fills are being used for some reason. There are 4 resolutions available for every bitmap and symbol. CC3 picks the appropriate resolution for the zoom level and displays that resolution. But there are times when for some reason it doesn't get the right one.

Click the hourglass in the left toolbar and check that you have these settings. "Automatic bitmap quality", "high". Clear the bitmap cache and Apply. If that doesn't improve matters temporarily pick "Fixed bitmap quality" and "Very high". Apply that, and then switch back to the Automatic bitmap quality settings.

If you are still having trouble after switching resolutions and clearing the bitmap cache, hit the Fill style resolutions (advanced) button and check that you have them set up like this:

On map 2 you probably have 2 nodes rather close to each other. Fractal lines can do that sometimes. Try using SIMPLIFY with a distance setting of 0 (zero) or som really small number, like 0.01. That will remove any that are right on top of one another.