Update: won the race! 5 laps, 35 miles, and great conditions. Kept NP on the screen along with the usuals - HR, avg HR, cadence, etc. Felt amazing at the start even w/a high HR of 170 (max is ~185). Kept an eye on NP and was around 95% of FTP and started cramping up around mile 16. Was able to fight through and continue to ride, never having to stop to stretch out the legs.
My nutrition felt dialed and hydration was on point, so just thinking I was going too fast too soon, but still held on for the win.
Thanks to everyone for the replies and advice!