What do you think Zhang Shi's relationship with Ma Gui was like? In what sense was Ma Gui his teacher? Was Ma Gui his host -- perhaps his first host?

Oooh, I'd never considered that, but I love that.

Given that Zhang Shi was a hidden, one-way parent figure, how much influence do you think he had on Zhao Yunlan?

I think whatever influence he had probably ended up confusing ZYL/messing him up a little. It's one thing if your dad is always harsh with you. It's another if every so often, unpredicably, he's kind. Mood whiplash.