Wait, there's a mistake. A big one, in fact. The guy in the countryside happens to be both Sonomi and Nadeshiko's grandfather, not father. Sonomi and Nadeshiko are not sisters - they're cousins.
As to the second question, I think, since Touya was a human - he had magic, but he was human, nevertheless. On the other hand, Yue is not human. I think that's why Touya can live without magic, although Yue can't.
And, I don't remember much of the episode where Song was captured, but if what you said is right, well then...it's stated that whoever does the most work gets the card...I don't think that requires magic.
Oh yeah...the old guy was confused when he saw the rainbow. Sakura told him to look outside and she created the rainbow. He said Sakura was like her mother - that is to say, mysterious. So, I think it's obvious that the old guy doesn't have magic. Unless you consider it dormant, that is.