Is non venomous snake bite painful?

Can be. Non-venemous just means no toxic/dangerous substance from the snake going inside your dbody, but the punctures from the teeth can be painful in certain areas of the body--sensitive areas. Fortunately though, these are often small and only causes minor discomfort, escpecially if you have high pain tolerance. Monitor for signs of infection...Swelling, redness, pain, puss etc... Check with your doc.
Depends. This depends on the type of snake, size of the snake and afterward, whether the bite site becomes secondarily infected. Pythons, boas, anacondas and other large snakes have teeth that are curved backwards to hold securely to their prey, so if bitten, pulling the snake directly off can cause severe pain and damage to the tissue area if not done correctly. In any way, be careful.
Can Be. I know someone who was bit by a Southern Black Racer who described the bite as quite painful.