[natch]

Actually your four don't capture my meaning. There is one missing.

3. Did he CONTRÁCT the disease? .. 5. Did HE contráct the disease?

Does that make it more clear? In other words, these sentences show the same "tones" (different from "tone"), but different stress.

You were saying tones are just stress, but they are not. The stress here is different from the tones.

With #3, the stress is on "contract"; with #5, the stress is on "he"; the "tones" (again in quotes because we don't really use that word for it in English, although I'm saying the underlying phenomenon is the same) are the same in both, although the stress is different.

You can change the tones and the stresses independently of each other, and when you change the tones of the syllables, you get different meanings for the words.

[_emacsomancer_]

I think we're using 'stress' and 'tones' to refer to completely different things. I think you're using 'stress' to mean something like what I would call 'focus prosody', and you're using 'tones' to mean what I would call 'stress'. But, in terms of the acoustics, 'focus prosody' is closer to Mandarin lexical tones (though not in function).