The alignment system is quite clear (though any individual GM can fudge/adjust them as they see fit... that is the beauty of the game).
This is how I rule on these matters in my games:
If you do an act that helps others and does not cause harm to others... that is good.
If you do an act that helps others but causes harm to others... that is neutral.
If you do an act that helps nobody (except yourself) and causes causes harm to others... that is evil.
The second is open to debate however, and this is where the problems on "acting within alignment" generally occur. In these cases, the GM must look at the reasoning behind the act, and whether the acting character knows what the consequences of their actions are going to be. If the character is doing an action for personal gain, or to further the personal gain of somebody they know to be evil... then the act is most likely to be evil. If they do the action whilst personally sacrificing something of their own (something that puts them at a serious disadvantage), then that could be a good act.
However... the look at the examples give:
Selling anyone into slavery is almost always an evil act. The only eception this could be argued if the person they are being sold to will improve the life of the individual, but even then this is shaky ground.
The baby thing... that is certainly an evil act... and if there was any doubt, the fact they "pretended" to help the blind mother nails the guilty verdict to them. The "help" they gave only furthered to rid them of any guilt they may be carrying and was a simple PR excercise to improve their own personal image as "good" people.
Torture is an evil act. Inflicting pain on others is not a good act no mater how you dress it up. Going as far as inflicting mental torture on the prisoners (i.e. the corpse etc) prior to any phsyical torture further proves this.
What you have here is a classic senarios where players beleive that a chaotic alignment (even chaotic good) is an excuse to do evil acts. Chaotic simply means that you do not follow the rules and you cannot keep a promise. It is not an excuse to do evil.
A lawful person will not break the law and will never berak a promise.
A neutral person will bend the rules and breaka few if it is necessary. However, they will also respect and follow the law as they regonise it's importance.
A chaotic person is unable to follow the law and will break it without a second thought. Likewise, they will never honor a promise as they hold no value in such things. Treaties and laws are there to be broken and do not aply to them. Promises are just words used to get what you want and nothing else.
If the character breaks the rules and is free with their promises so that they can help others - then you could argue they are chaotic good.
However, the examples given do not fall into this category... at least not to me.
The dedication to their home country suggests a lawful alignment if any. And the desire to do anything regardless of the pain it causes to other is evil. They are lawful evil. not chaotic good.
And a final thought... if the historical leaders who did great evil for the good of their people were good... what will that make the likes of Hitler a thousand years from now? (Just playing devil's advocate).