Ideally: to not reverse dox your merchants, hash the list entries.

The log message back, its a bit broad. Ideally its a zero knowledge proof and a clear amount, but that's hard and not mature yet. For now, I'd just make sure that its encrypted and strip any data that you don't need. (After all, everything you don't know is something you're not liable for and cannot get subpoenaed for.)

That's something that ultimately you just want to disclose in docs / faqs. Just be precise about what you keep and why. This is the business in the end.