You (anyone as well) have enough to work with.
Did he actually show you a cease and desist request and not let you keep it? Or do you have a copy of it you can share.
If he does not have a copy of it in hand they did not serve him. He also has to sign for it officially. There is a process. If that did not happen a court cannot honor it.
He looked at it, and there were witnesses, it's enough. Ad we have recorded the majority of the conversation as well. Should be enough to sue for damages of business and a few other fun things. But we're considering going a different route in the mean time.
You're going to sue for "damages of business"
Have you considered having a real lawyer laugh you out of their office or did you get a quote from prepaid legal?
Guess what, in America, you can't sue someone for what they say unless it is willfully and provably false, and that means you have to prove that they knew what they said was false. If you try to sue someone, you'll end up having to pay their lawyer bill, and probably get countersued in the process for the value of the goods that you owe them, plus damages.
Edit to add, I believe you will also have to prove that the negative / defamatory statements actually cost you business. At this point, if anyone is dumb enough to order from you, it can't be very much. Good luck proving a statistical variance of your purchases based on the posts of Bruno, or anyone else.