I've done dark eggs (Marans and Welsummers) and have not found a light bright enough to see anything useful. I can see the size of the air cell and that becomes easier at the end when the chick blocks all light, so I guess I can see something useful, but never any veining.
As for removing stinky eggs, I haven't found candling that useful. Instead, I take a careful whiff when I'm near the incubator. You can definitely smell a bad egg long before it explodes. Normally, they have hairline cracks that were not noticed when setting the eggs. When they smell, they usually also are weeping a sticky fluid that is visible, so you can find the culprit pretty easily and remove it.
I only had 2 or 3 that went bad all year (out of hundreds set), and none exploded. I have had bad eggs explode when I was not watching closely enough, that taught me to pay more regular attention to the incubator.
I would not bother candling the dark eggs, except to check the air cells. If you pick them up and examine them externally, you will find any bad eggs. Careful handling before incubation (to minimize cracks) will make stinky eggs a very rare problem.
