Re: Hands or cutleries?
You must see that Islam brings the entirety of life under the authority of Allah: civil AND domestic practices. Every culture has (and had) its own laws, but in Islam we believe these come from Allah.
As you say, you must take cultural context into account. This culture (or rules) that people extrapolate into sunnah perhaps came from Allah, but through the context of the culture when it was revealed. If Allah had chosen China to reveal his message then the prophet would have been eating with chopsticks. Unless we believe that the culture, eating habits, etc of Arabia were superior to all others, then we have to assume that whatever standards are native to a particular culture (as long as it doesn't conflict with non-cultural laws of Islam) are just as acceptable. I mean we are talking about a practice that is messy and not necessarily sanitary. If God even cares how we eat our food, surely he would prefer we it was clean and sanitary.