You are correct - In general, road signage in British Columbia is very poor, particularly when you compare it to the excellent signage in the United States.

There needs to be many more early signs telling you of changes in traffic - They're simply absent. I'm not sure if its budget, or culture, or what.

It's possible you were grilled at the border because you were only coming for a very short trip. I suspect it's outside the norm for a tourist to cross into Canada for only a few hours, to go to dinner in Surrey, then come back.