Incomplete Sevul

[Midgardsormr]

Visual telegraphs were in use during the Napoleonic wars. Essentially they were mechanical semaphore stations with telescopes. There is also the heliograph: a mirror that could be used to pass messages on line-of-sight on sunny days. The heliograph has the advantage that you can hide the signal from a soaring dragon.

City-state confederations seem like a likely form of political organization after a major depopulation event combined with dangerous territory. Infrastructure would be an issue with that kind of arrangement, as every city would be reluctant to contribute to national-level projects (laying rails for trains or building and manning telegraph stations). Those things could be created by private enterprise (like the powerful railroad companies in the US after the Civil War), or there might be tension between the local cities' interests and a strong national government that appropriates resources for inter-territory development.

Cold climate crops: wheat, potato, onion, most kinds of leaf greens, celery, barley. Probably others, but that's all that comes to mind immediately. Look up Scandinavian cuisine and see what they use; that's likely the same sorts of things that will grow in your territory.