Tangible Energy is basically in the form of the blood and flows in the arteries and the veins. Acupuncture tries to explain it and supports the theory of energy flow. What is the form of energy focused in the practice of Acupuncture?
According to me the base of Accupuncture is from Ayurveda. In Ayurveda the one of the concept i.e. "Marm" (Vital points) This some what realated to Accupressure and accupuncture is a innovation which is the furter step. At time of Buddha so many Boudh Bhikshuka went to China and they taught about the basic concepts of Ayurveda and herbal drugs. They developed well with some other concepts i.e. Energy channels like this.
Practice of acupuncture, need choose the acupuncture point ( xue wei) and also use the skill (technique), such as put plug twist and plucked et (ti cha nian zhuan, tan bo deng), that will be give energy for the blood flow or pain relief.
Regarding the biological basis, there is a connection between meridian system used in acupuncture and chakra system of Ayurveda in developmental biology as explained near the end of this article: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2644274/
Yes indeed, most certainly. They are both based on blind faith while medicine is based on properly regulated science. Not always 'well regulated' science but certainly better that a belief in fairy tales
Yes, that is in holistic approach to the human (body and mind as one and affecting each one, as well as organs and systems of human body are interconnected and affected each other). Also both not necessarily non-scientific, but rather pre-scientific (not studied closely via scientific approach).
The efficacy of acupuncture has been confirmed by the gold standard of clinical science - Cochrane Reviews. Both the basic and clinical research of acupuncture have met the gold standard of science as explained in http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2644274/