Istredd is definitely thinking about the time Geralt showed up and threw a monster head on the floor in front of him. That he had to deal with. It's not as if he can turn it off. "I don't need the tunic, the blood is fine, it's the rest." Why would the other parts bother him when the blood and corpses are just as bad? No idea, don't ask him, he's reacting in real time to new experiences!

"Don't judge me for being squeamish, I'm new to this." It's possible at some point in the future he'll have done this enough times he's more natural with it. This isn't going to be his last trip, that much at least is certain. He doesn't think Lucifer is being judgmental, ish, it could be him that's judgmental of himself. Typically how it goes.

"Fine, no, I'm here to learn, we'll ... do what will get the best price. That's the point. It would be nice to not be poor for a few days." Istredd frankly always had the Brotherhood bankrolling him and other interested parties. He is quite spoiled with that in mind.