You can also open the autosave file straight from the CC3+ file menu (open autosave file) so you don't have to dig around for it. Sorry for not mentioning it in my first reply, but beware that the autosave is only a single file, and may have been overwritten by something else if you have had another map open, depending on your autosave settings (the default is to pop up a dialog every 5 mins so you can chose yourself)

Note that this doesn't have anything to do with the pixel size (or file format), it is the Crop Image to aspect ratio and Restrict image to map border combination that ensures that the exported image only contains your map, and not white area outside it.

Hue is applied to the entire sheet, so there can't be a way to get the numerical value, because it isn't just a single colour you will be modifying. One part of the sheet may be green, another red, and the hue effect applies to everything so there simply isn't a fixed starting value. What you apply as hue is a modifier that will be applied to the colors on the sheet, so with a positive value, red will become more yellow, green will become more blue and so on. Look at the color wheel to anticipate the changes, the larger the value for hue, the larger the shift along the wheel. Remember, you aren't editing a single color by specifying its HSL value here, you're applying a HSL change over all the colors on the sheet. This is very different from just setting the current color in a paint program using HSL values instead of RGB.

When compared to the rgb matrix process, it's a different way of accomplishing a similar, but not identical thing. Hue operates on the HSL colorspace, and shifts colors along the color wheel. RGB martix operates on the RGB spectrum, and allows you to manipulate the RGB components of the color, and even express one color component based on the quantity of another component, something impossible to do with the HSL effect. RGB Matrix is more powerful, but also more complex, HSL can be easier to use to get more subtle tone changes.

Those spikes are miter joints, the issue happens when nodes are placed to create very sharp corners on wide lines. It happens more easily on highly detailed coastlines.

One way to get rid of them is to manually go in and remove some nodes from the coastline to fix it. Remember, it is caused by two close nodes at the base of the spike, there isn't a node at the end. And note that you only need to edit the coastline, which is a separate entity from the landmass. This problem doesn't happen to filled entities like the landmass is.

The second option is to just drop the coast outline altogether, and use a glow effect on the landmass instead, as this completely avoids the problem.

To elaborate a bit on JimP's answer here. Symbols are by default scaled to 1/1000th of the map width in overland maps. There are several good reasons for this, but if you want your symbols smaller, you can permanently change the default symbol scale for a map by going to :CC2PRESETS:. The value found here is the value that will be used when you click the set normal button Jim refers to. The "default" scale for symbols in general is 1, but be aware that trying to map a map of that size using symbol scale 1 will be quite a lot of work. The small symbols may not look as good either when the map is zoomed out.