Am I at risk for a potential workplace ADA violation?

Location: Georgia (US state)

I work at a popular chain restaurant. Not gonna say which one for privacy reasons, but you get the idea.
This particular location features dine-in service.
Today, a customer came in with a dog.
It was clear he didn't want me to see it, as he sat it in such a way on the table bench that it was difficult to see from most angles. I saw it regardless though.
Our restaurant has a no-pet policy, so I told my manager, and he said I should "Ask if he has its service dog papers."
I politely asked "Sir, do you happen to have that dog's papers on you?" to which he stood up and loudly explained how "it's illegal to ask that. This is my PTSD support dog, and you are violating the American Disabilities Act."
I'm quite young and new to the work field, and while I am aware of the ADA, I was unaware it had any such clause against asking to verify a support animal's papers.
Once again I say that I did not say it in a rude or demeaning way. It was a genuine question with the same tone I'd ask "Would you like a refill?" or "How was your food?"

I stammered and said "o-okay" before going back to my manager to inform him of this encounter, to which he told me he'd look this up while I brought the customer his drink.
Prior to the man sitting down he had already told me he wanted a Coca Cola, so I filled a glass and brought it to him.
Upon setting it down on the table, he exclaimed "What the fuck, dude?!"
Shocked by this sudden harsh language, I just stared at him for a second, and he followed up with "Are you doing this shit on purpose?"
I calmly asked him what I did, and he said something along the lines of "You put the glass down hard! You're clearly trying to trigger my PTSD on purpose!"
I will admit that when I placed the glass on his table, it did make a sound, but it was by no means noteworthy or excessive, nor was it any louder than when I place drink cups on any other table.
I told him that I didn't mean to, at which point he started loudly yelling at me, saying things along the lines of "Alright smart guy, you think I don't get what you're doing?"
He was making a scene at a time in which another family of 9 people, including their toddler, were dining in.
Knowing this was out of my control, I called for my manager, and he demanded some sort of company paperwork number. Truth be told, I am illiterate in legal terminology, so I have no memory of what he asked for.

Upon getting the desired information from my boss, he left the restaurant without even paying for his drink.

I can't imagine I could be in the wrong for such an encounter, since all I did was ask him the question my boss had specifically requested I ask (being a request the dog's paperwork), but all the legal answers I'm finding online are very vague about the exact laws and repercussions, some saying it's illegal to say anything else than "the two questions," while others say it's fine as long as you don't use the answer as a reason to discriminate.
I'm tired, I'm scared, and I want a forward answer.
Am I, my employment, or my place of business in any possible legal dangers, and if so, to what extent?