1. Can a figure in a street location see any other figure in a street square? I assume yes but that shooting is limited by the range of the gun.
Yes, you are correct.
2. How does Barricade (Huckster spell) work with line of sight if the caster is in the street? I assume that if a person in a building can see the figure in the street the figure can see the building in return (although as mentioned one cannot shoot into a building).
You are correct. Basically line of sight isn't going to extend any further than the buildings on either side of the street square you are currently on and the street squares on either side of that. So if you are on a street square, there would at most six buildings in line of sight.
3. Can you see a building next to you? This comes into play when a person casting Barricade is in a building, is he able to cast in on an adjacent building? In a similar vein can I cast Hell's Fury/Summon Serpent/Smite from one building into an adjacent building? Can I cast one of those spells from the street into a building?
Line of sight doesn't go from one building to an adjacent building. It does however extend to the building across the street. You cannot cast a spell into a building if it targets a specific person like Hell's Fury. It's assumed that the sun is up and that you cannot see into the buildings.
4. What buildings can I see across the street while in a building? This comes into play with Barricade (grrr, that spell).
Just the one across the street.
5. In reference to Dynamite, are the diagonals considered adjacent (street to building, or building to street)? Can I throw it from one building into an adjacent building? Are diagonals considered adjacent in terms of adjacent squares taking damage?
Diagonals are considered adjacent, but you cannot throw dynamite from one building to the next. You can throw it from a building into the street or from the street into an adjacent building (including diagonal).
Thanks for answers in advance,
Also, the graveyard is not considered a "building" as far as the can't shoot into a building ruling goes. You can shoot into the graveyard from a street square.
I have added these questions to the FAQ on our website. Let me know if you have more.