(1) There is a faint circle around the constructor you use to create the starbase. That circle marks the limit of the range. You might have to zoom in to see it. When your constructor gets close enough to a resource or relic a line will appear from the resource/relic to the constructor indicating that the resource/relic is now in range. Again, you might have to zoom in to see it.
(2) No. The only benefit you might get from a resource/relic outside the starbase range is if you later manage to expand the range of the starbase to get them inside.