I'll give you two sets of replies:
A. What you should say, take it from a trained psychologist
B. What I would say (or have said.)
1."What are you thinking?"
A. "I'm thinking about *whatever subject does not matter* and that I really would like to hear your opinion about it."
B. "On my job."
2. "Do you love me?"
A. "Of course I do, otherwise I wouldn't be with you. Why do you ask?"
B. "If I didn't, what do you think I'm doing here? Admiring your cute ass for 2 years in a row?"
3."Do I look fat?"
A. No, certainly not, you look great. You have a very beautiful and sexy behind//legs/whatever. But if you feel like changing soemthing...maybe you would *also* look very good with a little bit more muscles on your ass/legs/whatever. (The *also* is very important - don't suggest the person would look *better* other than the way he/she is)
B. They never have to ask, I suggest they should exercise more long before they even start to get fat
4 - "Do you think she is prettier than me?"
A. "Well, he/she is very pretty. But his teeth look to much like a toothpaste commercial, a bit too superficial. (Focus on something that is not so pretty, everybody has something). You are much prettier."
B. "Yes, but that doesn't change anything."
5. "What would you do if I died?"
A. "I don't know...I would be devastated. I'd rather not think about that now, it's too horrible."
B. "I have no idea, since it hasn't happened yet. Maybe we don't even know each other when that day comes."
6. Have you ever fool around with NN?
A. "Yes, a long time ago I had this brief affair with NN, but he never meant anything special to me/it was a mistake/I never felt anything for him that's even close to what I feel for you."
B. "Yes, and that was great fun, he's really good in bed."
On the serious side: Don't start a relationship with a person asking any of these questions unless you like to take the role of constant provider of ego-booster, confirmation giver and support person.