Chewing with your mouth open is NOT RUDE.
It is simply par for the course such as picking your nose on the Hong Kong.
Reading a newspaper at the table is NOT RUDE.
Generally speaking, it is not rude to pull out the Chinese paper during dim sum after you've finished eating. It does not matter if others at the table are still eating.
Pouring yourself some tea first before pouring tea for others is RUDE.
It is extremely rude to pour your own tea before pouring tea for others at the table. Fill the cups for those near you even if their cups are still quite full, starting with the oldest people. If nobody around you needs more tea, then you can pour your own tea.
Extending your pinky finger outwards as you hold your tea cup is RUDE.
While the British may do this as they sip their tea, Chinese people don't.
Reaching across the table to get at a dish of food is NOT RUDE.
If you can reach the food, it is best not to trouble your dining companions with the ritual of passing the plate around. If you can't reach a dish, make an obvious gesture towards it and someone will offer to put some in your bowl.
Putting food in other people's bowls even if they don't want it is NOT RUDE.
You are actually demonstrating your good nature by serving others instead of yourself. Usually, there is one person at the table who is an obvious target for any leftover food.
After dinner, pulling out a toothpick and picking your teeth is NOT RUDE.
This is one of those things like chewing with your mouth open or picking your nose on the subway.
Not offering to pay for the meal because you were invited to dinner is RUDE.
The unspoken ritual is for you to fight with the host over the bill and mercifully concludes when you pretend to reluctantly acquiese and vehemently proclaiming that you will get the bill next time.