Maybe the key should be to one side or below the whole map, since there isn't a lot of room in the map, though it's really too early to be thinking of the key. It's more of a labelling process at the end of the drawing.

I can't see what style you are using because it's so huge the textures are too small to identify, but the answers to some of the other questions could depend very much on the style and the arrangement of the sheets.

If there's not very much happening between the points of interest, you could do several dungeon scale maps - one for each point of interest?

Don't get caught out by failing to check the time. This livestream is an hour later than usual.

There is a pink glow on the SYMBOLS CLIFF sheet. I've hidden it in this screen shot.

What I've suggested is basically a replacement of the standard bevel, but using the bevel to get the shape to draw.

As for the issue more generally - artefacts are likely to occur with quite a few of the effects if the polygon extends a long way outside the edge of the rendered area, since some of them rely on the render engine being able to 'see' the whole polygon. A small distance outside the map is ok, but once you get beyond a certain distance away it all goes a bit wrong.