Yes, you can feed nucs. I would not do silly things like add scent. (You know, the stuff they say is important to keep bees healthy.....now that nectar and pollen is not doing the job after millions of years.
) This is like ringing a dinner bell for other hives to come and get it.
If your using a nail, the holes are probably too big. Syrup should not be dripping out of a jar in the manner you describe. I use a push pin and tap it with a hammer to just get the tip through the lid. Anything beyond this small hole size is not needed.