Did you find "suspectful" in you dictionary? I didn't.
A skeptical/skeptic person is an intellectual person who doubts other's opinion. A suspicious person is a person whose behavior causes people's suspicion.
I am sorry for the 'suspectful', it was supposed to be 'suspect'. Webster says 'suspicious' can mean both DISTRUSTFUL and 'tending to arouse suspicion'.
All the examples you brought up in the sense of 'skeptical' refer to things as subjects. Can't we say 'suspicious' about a preson so that it will mean 'skeptical'?
I am afraid our understandings about 'skeptical' would be different. 'A skeptical letter' is not 'a suspicious letter'. We send a skeptical letter to a journal editor to argue against some articles of the journal. We don't send a suspicious letter in this case.
paco
[PS] As to your 2nd question, sometimes people use 'suspicious' in the sense of 'hav
I understand 'sceptic' letter as 'controversial letter' in the latter case. That's why you were ellegedly going to fight against it, isn't it?
Paco, I think I understand you. Suspicious is the passive of sceptic. Is that your intention? I mean if someone is sceptical about someone else, the 'someone else' is suspicious by 'someone'. o_O
Yes you are right. "X is suspicious of Y" is "Y is suspected by X". You can say also "X is skeptical about/of Y". But 'skeptical' is originally a philosophical term meaning 'be among Skepticis (Greek philosophers who doubted any established ideas). So it implies something intellectual, while 'suspicious' is rather a common adjective.