What are my options if I want to install a bed levelling sensor capable of operating at 100 °C?
Have you considered using or adapting Prusa’s P.I.N.D.A. V2 or SuperPINDA? Seems that within some bounds they’ve solved the temperature compensation issue.
The older P.I.N.D.A. V1 sensor seems to be temperature-sensitive. See more information in P.I.N.D.A./SuperPINDA Sensor testing article of Pruse Knowledge Base.