My understanding is that radiation for PNI is standard. My post surgical pathology report also showed PNI so they gave me yet another round of radiation even though I had already had the "maximum" 70 GY the first time. [re-radiation is becoming quite common since CyberKnife] The Dose of radiation varies with location and I'm not competent to guess about yours.
It's always disappointing to have to undergo even more TX, but trust me, it's far better than having the cancer come back.
Congratulations on a good node report. That's a very good sign.
Keep the faith
Charm