One problem could be figuring out whether you were really illegally detained. Just because a cop withhold's or lies to you about his reasonable articulable suspicion (RAS) does not mean he had none. Courts seem to tolerate cops lying to suspects (google permissible deception), and I've never seen a court case or statute that requires cops to tell their RAS to the detainee.
If Florida has a Sunshine Law, also known as a Freedom of Information Act, you could always request various records like whether there were any 911 calls reporting a person behaving suspiciously, or the gas station clerk reporting he thought you might have stolen something, the cop's field contact notes, etc.
If there were no calls, then the cop is going to be in a position of having to explain why a fella walking home with a cupcake is suspicious, meaning what crime he suspected you of.
An alternative would be to just write a formal complaint, skipping the FOIA. It might be there are no revealing recordings or records, especially if the cop was just driving along and decided to seize (detain) you. Under this approach of just writing a formal complaint, you just assume the cop had no RAS, and make him defend himself in any internal affairs investigation. If he had genuine RAS, he'll be found innocent of wrongdoing. Heck, even if he didn't have RAS, he'll probably be found innocent of wrongdoing, but at least the cops will know they have to be a little more careful because some citizens really do know their rights. In any event, it is not your responsibility to do all sorts of investigating to find out what was going on. If the cop wants to not reveal RAS, be vague about it, or lie, making it hard for a person to judge the legality of his seizure, then let the cop defend it after the fact. You can dig if you want to (FOIA). Sometimes it turns up very interesting information. But, its not an obligation on your part.
Several points that jump out from your OP:
- Likely illegal seizure (detaining you)
- Likely illegal search and temporary weapon seizure (if he doesn't have RAS to detain you, he doesn't have authority to search and temporarily seize your gun)
- Likely illegal identity demand
- Likely illegal identity document demand
- Cop yap and yammer against self-defense tools
- Threat about taking reloading as a hostile act and "consequences". This is absurd. If he releases you, he has no further authority over you. If he is scared of a citizen reloading, he can hide behind his car until you leave. (this is an angle for a complaint, I definitely don't recommend actually reloading in front of a hostile cop.)
You can always talk to a lawyer about a civil rights lawsuit.
If you go for the formal complaint, realize that the police will probably deny any wrongdoing. That's fine. The point isn't to get them to admit anything. The point is to:
1. Establish in writing a history. A paper trail. In civil rights lingo, you are documenting a pattern of abuse, if such continues.
2. The cops will know they have to be careful about who they arbitrarily seize. "Oh, $hit! Somebody actually does know their 4th Amendment rights! Now, we gotta be careful, dammit." This alone might guarantee no more stops while walking to the gas station. Just understand that even if the cops claim nothing wrong was done, they will get the point. A good supervisor will know the score. If you make enough noise, a supervisor might well tell the cop, "Well, you'd better make sure 'nothing' never happens again."
If you need help or pointers on writing a formal complaint, just ask.
Do not accept an invitation to come down to the police station to discuss it. Cops love verbal complaints because they can disappear down the memory hole. Written complaints often trigger formal investigation requirements. And, you gain nothing by discussing it. In fact, you can expect, whether you talk in person or on the phone, to be treated as a bad guy with plenty of questions about you. Just realize that your 1st Amendment right to petition government for redress of grievances does not require you to talk verbally. Your complaint will be complete. It would require no discussion. If the police have questions to clarify some aspect or circumstance, they can always write you.
In any event, take some time to let the memories come back to you. Some folks have success writing out the events several times. More comes back to mind as you write it out each time.