Yukkuri Hell is a mixture of Human Spiritual Hell and the Robot Physical Hell, basically bad yukkuris that hadn't died yet, may first be sent to the "physical" hell, and be tortured in horrible way, only to later be killed and send to the spiritual hell for the rest of eternity, where their minds would never be able to break so they could avoid the painful "reality" and every form of abuse would then be followed by a forced injection of boiling orange juice that would quickly heal them while making them feel pain.
Doubt it, if human hell is ruled by demon, onis, etc. why should the Yukkuri Hell be any different in the administration? specially when their main source of punishment comes from humanoids in real life?
If Satan were a Yukkuri... Satan: "Welcome to your eternal damnation to...what are you doing to Mister Braids? Shtop it, eajy! Yunyaaa, let Shatan take it eajy! Yunyaaaaaaaaaaaa!!" Me: "Happiness!"