I'd make a formal complaint against the store manager.
As in goto a magistrate and swear out a warrant or press charges. Shenot only treated you like a criminal, she tried to turn you into one.
You were falsely accused of a crime. A false report was made to the police.
FIrst, though, I'm thinking it might be smart to FOIA the 911 call and radio traffic. If you swear out a warrant first, the police will withhold the recordings as part of a current criminal investigation. Get the recordings first, then swear out the warrant.
Off the cuff, the police seem to have acted within the bounds of the law. All except the ID part. If you were reported as an attempted gun-concealer, that would give police RAS to detain you, I'm thinking. Since the report included belligerent, the police would seem to have the second element of Terry--reasonable suspicion that the detainee is presently dangerous.
The false accusation from the store manager absolutely cannot be tolerated. Its only by the good graces of the officers that your situation didn't get worse. If you had not persuaded them the accusations were baseless, you could have been in hot water. Also, thank the stars you got honest cops. Dishonest or anti-gun cops like Legba ran into could have made it much worse for you. Also, consider that if the store manager is willing to lie this much, its only one tiny step more for her to say you actually touched the gun or made a threat.