Unfortunately SetSunActive(0) affects the whole scene (everything drawn in Render3D()) ....and using SetObjectLightMode(ob,0) turns off the sun and the point lights too but you probably want to keep the point lights in your interior scene.
A couple of options I can think of quickly:
1) Use a custom shader on your interior walls that is only lit by the point lights. you would have to pass the point lights to the shader but this way you could use way more than the built in 8 if you wanted to. Alternatively you could make the exterior shader custom and apply a sun value and direction but turn off AGK's sun when rendering the whole scene. That way...your sun will only be applicable where you want it to be.
2) You could do 2 render passes - Turn the sun on and render outside areas then turn sun off (SetSunActive(0)) and render the interior spaces.
Personally, id go down the shader route and then you can even have spot lights or specular if wanted too.
