2 If maths can have a 'second derivative', why can't language? If X, Y, and Z are 'bad', 'worse' and 'worst', Z is still worse than X - but it is worse to a greater extent than Y; Y is 'the lesser of the two evils'.
3 'Ago' is meaningful in a context where 'now' has a meaning - typically in direct speech (though also in, for example, journalism'. So '"I did it two weeks ago", she said' but 'She said she had done it two weeks before their conversation.'. And if it's the conversation that took place two weeks ago - 'We're seeing the customer tomorrow, and she still hasn't written that report. She told me two weeks ago that she would do it before the meeting.'
4 'Where is the US going?'