When you install the update you will probably get a message that tells you you have a newer version installed. If you do, just ignore it and carry on installing the update.

Most of the things you are highlighting as being an issue are down to sheet effects. If you put an Edge Fade, Inner sheet effect on the snow you will be able to show the bevel on the coast. You can also use one of 3 colour modifying sheet effects on the swamp areas to change the colour. These are (in order of ease of use) the Adjust Hue/Saturation, Colorize, and RGB Matrix Process.

I recommend using all the same mountains and hills if you are going to use a different style. the hills really don't look that bad, even if they are paler. In fact it is better that they are paler than darker than the land since it makes them look like bumps rather than hollows. You can always replace them later using Replace in the Symbol Manager if you still don't like them.

Sheet effects are always a personal taste. You can learn a lot by experimentation.

Looks great :)

The grass patches should be the same scale as the grass fill as long as they are set to the default symbol scale of 1. I have noticed that there are points as you zoom in and out of maps with a mixture of fill and patch that the patches sometimes 'click' to the next resolution slightly before the fill does. This shouldn't be a problem when exporting as all will be exported at the same resolution, but it can look like the patches are wrong in the CC3 window at certain zoom levels.

The other possible mismatch is if you are using the fill from one style and the patches from the other style. Creepy Crypts grass does not exactly match Forest Trail patches, and same vice versa. I personally prefer the Forest Trail grass texture and patches, but it's down to personal taste in the end.

The choice of trees is up to you, but something to bear in mind when borrowing things from other styles is that while you might love the look of the trees from an alternative style that doesn't mean they will automatically be the best match for the style of the map you are making. If you don't like the combination maybe try a few other styles, including the trees native to the style of the map. Similar styles usually work better together than vastly different ones, and it is usually easier if the two styles have a similar colour scheme.

It sounds like you are using a style which has separate coastlines. Look at your sheets in the sheets and effects dialog. If you have a sheet called LAND and a sheet called COASTLINE then to adjust only the coastline thickness pick the COASTLINE sheet and hide all the others. Then you can pick the coastlines and adjust their width and reshow the rest of the sheets.

A general note that might help in the future - if a polygon has any kind of line width greater than zero the fill will vanish and leave just the outline.