TC, I am glad to hear that you did not end up in a small room with bars, but I don't know that you could exactly call this a positive encounter. I am not trying to be critical of your demeanor, and none of us know exactly how we will act until we get into a similar situation, but there are several things I noted about your story that bothered me a little.
Cops have a way - actually a lot of people have the same way - of using interruption as an intimidation device. They start talking over you aggressively in order to get you to comply with their wishes, whether it be an LEO or your girlfriend.
This is the point in the encounter where you need to regain the initiative. Just because he interrupts you and becomes a little aggressive, you are not obligated to obey, or even to respond in haste. Stay calm (as calm as possible!) and tell him you are not required to show ID while on foot. Then (this is the regaining initiative part) ask him what crime it is he suspects you of committing. Now he has to respond to your request!
Second, as GunLawyer001 has already pointed out, his rooting through your wallet is a big problem. Most cops I have encountered treat wallets like Superman treats Kryptonite. They absolutely refuse to touch them, but demand that any ID be removed and handed over. This keeps them from getting into trouble over the $100 that
was in the wallet, but isn't now.
I would have put up a much larger fuss about being disarmed. As soon as that gun comes out of its holster, the safety level of everyone in the area has just gone down several notches, and these guys need to be reminded of that. Personally I don't think it has anything to do with safety. If he were truly concerned about his own safety and you using the gun on him at any time, you would have been looking down the barrel of his own gun with him screaming at you to get down on the floor. No, it has everything to do with a power play, intimidation, and assertion of authority. This is not to say that you don't have to comply with his order, but you can make sure that he knows you know the real deal. Put the onus on him to explain to you why exactly you need to remove your gun. He has evaluated you already before approaching you, so why now does the gun need to come out and be unloaded? If he really thought that, it would have been the very first thing he did.
Again, none of us knows exactly how we will act in a given situation until we are in it. Going home alive and free is always important and you accomplished that. I am typing my thoughts here in the event that someone else finds themselves in a similar situation, they may have some preparation with some options on how they can act. I am in that Home Depot on a regular basis. I have been in there OC on a number of occasions. I will be contacting the store manager today to tell him the people in Lowes have never bothered me either and that if he doesn't like guns on customers, I will take my considerable home renovation budget elsewhere. I will also follow that up with a letter.