If a ship or ships are within visual range (I can see them), the targeting reticle should be able to get a lock on them/it.
As you can see in this screen grab, there's an enemy sitting off to port quite a distance away. I can't see it by my sensors tell me it's there. The squadron of scorpions coming in, my sensors have n idea about yet I can see them.
http://i4.photobucket.com/albums/y131/SG1fan1/iseeyou_zpsf3bf28b9.png
Also, If I'm far enough away to shoot and destroy an enemy, I should be able to collect loot from the kill from as far away as I am. Just saying.
Comments
The problem you're having is that the targeting setup doesn't register fighters, mines, and other small objects by default, in order to reduce 'clutter' on the screen (lots of target reticles leads to UI lag). There is an option within your settings that allows you to activate targeting for those objects.
Edit: As for the loot, I agree. Should be able to pick it up from 10km away.