CQD as Troubleshooting tool??

To be honest, I'm not answering any of your questions but I'm still going to reply. :) For troubleshooting Skype for Business audio quality issues, we have this excellent tool called Call Analytics. It can be used to determine if user has used integrated microphone, if there has there been jitter or packet drop etc. More about Skype for Business Call Analytics and how to enable it can be found here:

https://techcommunity.microsoft.com/t5/Skype-for-Business-Blog/Introducing-Call-Analytics/ba-p/57309

Oh wait, I kind of have an answer for your 3rd question. Call Analytics can be used to see traceroute / path per session.