I know it isn't my thread, but I hope it is ok for me to answer some of these questions. I am answering from my point of view though. CrockyBetter might give different answers.
Have you ever been in love
no
Do you ever feel sad you don't get to enjoy sex or doesn't it bother you?
no, doesn't bother me in the slightest. Why should it? I'm sure there are lots of things I enjoy which you don't. I could ask (if you are not a marathon runner) Do you ever feel sad you don't get to enjoy marathon running?
Do you ever witness other people's grand passions and lusts with either pity or envy? Or do they just not interest you?
occasional pity, if its all going wrong. No envy, some boredom. I am interested in if my friends are happy or not, I'm interested in how everything is going for them, including relationships. But I have no interest in relationships as such. The subject is quite boring in abstract, even if the welfare of a friend is interesting
If you had the ability to add strong physical desire to your life, would you do it? Definitely not. Sounds like being shackled. I have no interest at all
That's my answers! If CrockyBetter comes back, they might answer differently