Thank you guys, for all the positive comments!

Modifying the rings really improves the map but the way I did it was a veeery slow (editing 10 layers one by one is simply too much) and stressful (the moment I realized I had to fix the rings on like a quarter of the map was awful) process. Maybe for a smaller map (or at least, one continent only) that would be quite useable, though.

Ramah, I cannot take much credit for the "Final printed" looks as I used the paper from a real old map for it and just pasted my map over (after cloning away the thing that was originally showing).
Regarding the lines and their outer glow, though, you give me a nice idea. If I put them below all the labels' layers then the labels would be wholly visible and erase a bit from the grid lines (cause they have outer glow, too) but that won't be a problem. Since because the lines are straight, our eyes would see them straight even if they have some tiny breaks. And the outer glow is there (as Ascension mentioned in the Tutorial) because in general it's a characteristic of the antique maps to have many labels and details that are easily readable.