NFPA codes are not law!! NFPA makes recommendations.
If a fire marshall, fire inspector comes to a private residence to inspect your "stash" he needs PD and a warrant, which means there is probable cause that a law is being broken. Regluations for a business may be enforced by the F.D.
As far as your insurance coverage, it may be best to check with your ins. agent. They may feel different about NFPA recommendations. Don't forget to use answers like, not very often, occasionally, sometimes.
There are a lot more dangerous items in every garage and storage shed then the amount of powder and ammo stored by the small number of serious shooters and I don't see a door to door "search".