As far as securing the cable every 4 1/2 feet, some jurisdictions do not rigidly enforce this in attics feeling that it is better to allow the cable to move when the insulation is jammed in from below or the cable is kicked by someone crawling in the attic.
Your loose cable is a violation, but I personally wouldn't lose sleep aver it. I'd be more concerned about the quality of all splices & connections.
You might want to do something about the cable over the ducts, I have heard of cases where the vibration, slight as it is, wears through the jacket & insulation.
Few things are harder to put up with than the annoyance of a good example.