Ben tried to kill her because he saw that she was not one of the good ones. Upon her saving his life, he assumed that she might be, but when his thanks were met with scorn, he thought otherwise.
He attacked her because she called the Others killers. Before he hit her he whispered "you insult us."
He may have whispered "We're scientists" as a retort to her calling them killers.
Not likely because before Ben blows a hole in the time capsule in the Orchid to get to the donkey wheel, he told Locke that this was another silly experiment the DHARMA Initiative worked on. This would indicate that he and the Others are not scientist as the DHARMA Initiative are/were.