Upvoted you back to zero. Let me try to poke a few holes, in good will.

What's the bad thing that we want to avoid?

If you just look at the behavioural instead of the experiental aspect of suffering, this already eliminates anything that could be normally understood by the word.

I don't like it when other humans experience things which are extremely contrary to their preferences

Preferences do not depend on the existence suffering, although suffering seems to depend on the existence preferences.

I feel no altruism towards the paperclipper, because while it's intelligent it is not a Person to me.

Taboo person.

In other words, "suffering" is when an intelligent and empathetic object does not get its preferences fulfilled.

Are you saying that nonempathetic human beings can't suffer? I find that claim bizarre.

humans with less empathy are less person-like within the semantic framework constructed above.

I'm a human being with less empathy, and I'm ready to protect my preferences, so be careful ;)

I think that if unstructured idle thought produces something that seems close to correct then, with sufficient thinking and modification we could come up with something that is correct.

With the current state of science, I personally don't think we need to define suffering any more than we need to define colours. Once we know what happens in the brain when a person reports they are suffering, we know what suffering is and how to measure it.