I did hit a PR on squat but full disclosure, I used knee wraps for my first time. I went from 455# to 475# but could easily throw on more weight without hesitation. I video my heavy singles and later sets on volume days and watching the video I can 100% say I had plenty of headroom left.
In terms of how I felt, hmmm... well physically I was pumped like you read about. My arms and forearms were out of control pumped. That doesn't happen normally.
I didn't feel nauseous. Can't recall that feeling once. I do feel anxious in general these days so I'm not sure on that one. I felt aggressive though. I felt like attacking the weight rather than approaching the weight. You know the phrase 'moves with a purpose'? That was definitely me that day.
I'm assuming that I'll get better at pin pointing specific details about halo as I take it more. I'm sorry I didn't have a better description for you. I'm going for a heavy 5 X 5 DL tomorrow and hope to see a solid effort and good numbers. I'll let you know how that works out, should be a good one.