Glad to hear you had a terrific day today. Glad everything worked out for you.
Just want to correct your #1 above: Cops do care. They care whether you are likely to be a criminal or engaged in criminal behavior or about to commit a crime. Seeing as you did not pose any threat of criminal behavior, they may have remained wary, but accorded you the appropriate level of deference for law abiding citizens. But saying they don't care is really inaccurate. Kinda like saying they were careless cops. I'll wager a Morgan dollar that all three went up one or two colors on the awareness scale when you boys walked in, and remained in a heightened state of alert until you were no longer in the location. They may have said nothing, nor given any overt outward sign, but rest assured, you were still on their radar.
People with big mouths are everywhere. I've often wondered why more of them do not have powder burns on their lips from shooting off their mouths as much as they do. Fortunately for me, I tend to be real quick with a retort. I can sling rhetoric with the best of 'em. Mostly, those folks with more mouth than brains can be simply ignored. To the mother who said to her kid that she'd get you to do something with her kid because you have a gun... I'd have told her, right in front of everybody there... "Look at what you just told your kid! You just threatened him with possible deadly force for misbehaving. You really want to use that sort of threat on your kid lady?" Or just substitute the word gun with penis and ask her how she thought it would be appropriate in any fashion whatsoever.
As for the guy who crowded you, I wouldn't have let it go as long. Once he started asserting his presence, I'd have locked my eyes on his and said "Excuse me!" If he didn't back off, I'd add "Mind stepping back just a bit, you're uncomfortably close!" This one is a bit harder because I don't know how he closed in, or what his demeanor was. Being the smart ass that I am, I might have said "Look mister, if you wanna get close to me, you'll need to wear deodorant or maybe shower in the morning!"
Every situation is different, and you will learn to cope with different scenarios as they present themselves. I am blessed with a background in radio, so have a penchant for glib responses programmed in and hard wired. As you OC when you go about your routine business, you'll learn effective ways to cope with different situations. I don't recommend the glib reply that I'll throw out there, but have some experience regarding what I can expect to get away with. Then again, I've got at least 40 years on you! I've had practice.
Think about what happened today, what you might have said, and how to respond to that same sort of situation in the future. Remember what you come up with, and start building a mental library of responses to different situations that come along. Eventually, you'll be quick with a quip and ready to articulate a response to nearly every situation.
Good luck, and stay safe out there.