Is Di Renjie's supervisor the historical Xue Huaiyi?

Yes, Xue Huaiyi was the leader (lover) of Wu Zhao, and was once the director of Tang Ming (or Vientiane Holy Land). A few years after it was built, Xue Huaiyi fell out of favor and burned Tang Ming. Wu Zetian was very angry. Soon, killing Xue Huaiyi was still a mystery, but soon, Wu Zetian ordered the reconstruction of Tang Ming, which was completed in the first year of Long Live Tian Tong, nearly 100 meters high! Three floors, with spring, summer, autumn and winter below, twelve o'clock in the middle and twenty-four solar terms above. The scale is roughly the same as that of old Tang Ming. So it was specially changed to Long Live the Sky.

Although the film is the same, there are many deductive parts. I suggest reading The Book of the New Tang Dynasty, The Book of the Old Tang Dynasty, Learning from the Same Resources and Tang Yaohui.