The game does not differentiate against how new your character is for most things. All that really changes as you progress in terms of how the game treats you are the raids on your home, and some difficulty (starred enemy) changes as you go outward from spawn. What has changed is that enemy have had an AI tweak so the multiple enemy work together better. Before, the large groups of dwarves were just each doing its own thing, now they band up and sort of coordinate. The world is just more dangerous now, regardless of your 'level' or time played on the new character.

I am with you. I have not found a good way to prevent the occasional boat breaker from getting through without an enclosed and gated building. If you do that, they break the building or workbench or something else. I have moved to an earthenworks dock (raised terrain, sloped shore, shallow deconstruction area) with a workbench they can't reach (due to raised terrain) and I just create and destroy boats on demand. So far, nothing else really works 100% for me. I don't like breaking the boat every time, but the game mostly demands it.