So, I spent 2 hours trying to troubleshoot this before I posted and within minutes of posting it we figured it was a PC connected to the network causing it. We had unplugged all the systems and now it's working reliably. I re-ran the proxy in debug mode and am seeing far fewer requests. I'm thinking one of the systems they unplugged was causing the issue.

So, once I verified I could boot over PXE (tested 10 times) I then tried to test the USB drive. Found it is still not working. I get the Boot menu but then a black screen after selecting CloneDeploy or Console.