When you say "hide all your layers...", do you actually mean layers, or are you talking about the sheets?

Also, hiding the map border (The map border is on the MAP BORDER layer, and the BACKGROUND sheet) can in some cases have unforeseen consequences, because CC3+ uses the map border to calculate the extent of the export. I have seen cases where that resulted in a temporary image ImageMagick couldn't convert in the final step, so please try as roflo1 suggested and do a rectangular section export instead, and see if that gives different results.

While not a good thing, this is far less serious than the browser like to claim. In this case it is just an expired certificate (but otherwise a valid one), so it is safe to ignore the warning and proceed. Certificates always have a set expiry date, so an expired certificate doesn't have anything to do with hacker, and the message that the information isn't private is actually a lie, because even an expired certificate encrypts the connection.

Of course, ignoring browser security warnings IS NOT a good thing, and not something that should be done unless you are absolutely sure it is safe to do so. Although it is surprisingly often completely safe (as part of my job, I have to do it all the time), it could also mean that there is indeed a problem, like a hacker playing man in the middle or having taken over DNS and redirecting you to a fake site. If you are even just the tiniest bit uncertain, wait until someone has fixed the certificate which should happen soon.

I wrote a blog article about ways to search symbols:

If you're doing overland mapping, there are generally symbols available for marking spots on the map in the :CC2BO: category.

Have you considered using a different style of roads? Those dashed lines works on overland maps because they're only representative of the feature, but on close-up maps like these, they come out looking a bit out of place. Maybe a dirt brown fill with a small edge fade instead?

Most scale bars are 100, but there are exceptions like the style from that thread, where it is 200. Some styles also have multiple lengths, like the Schley overland style which as two at 100 and one at 200

The easiest way to check the scale of it in any style is simply to place it (Make sure the current symbol scale is 1) and measure it using the Info->Distance tool.