This is exactly what I've been doing when studying mathematics! From letting my mind wander down to just staring at a definition and be 'genuinely curious' about it. In fact one of my favourite activities is to ask "What motivated this definition? Assuming these motivations, what definitions would I've come up with? How do they relate with this one?". It's the sort of exercise that feels important and meaningful to me, but I don't think I know anybody in my circle of friends who ever gives it a try. So I'm very happy to see it acknowledged!
Examples one and two are normal situations and people should know how to respond to them. The general principle is that when given an open ended question, don't aim to answer it in full, but make a small contribution and let the conversation flow.
Computational unkindness:
"What do you want to do? I'm completely fine with anything!"
"I've heard about X, I'd love to visit that place!", or "I don't know. What's a good place to hang out?"
Responsibility Offloading 1:
B: "By the way - feel free to throw me out any time! I've got tomorrow off, so am flexible, but just let me know when you've had enough of me"
A: "Hmm... I usually go to bed at 11pm."
Responsibility Offloading 2:
"Do you mind if I smoke?"
"Yes, I do mind people in a 10m radius of me smoking!"
Ok that was a joke. But you can still convey irritation and offoffload the responsibility at the same time. Say "Sure..." with discomfort in the intonation.