This is correct. In scientific terminology, a theory means a concept which is based upon a preponderance of facts which are used to explain and predict phenomenon and is concomitant with other theories which in turn are testable and make predictions upon which such tests are based. To say that something is a "theory" in a scientific context is to simply say it has been proven, and this is not the same as the layman understanding of a theory as an educated guess.

This is an argument from incredulity. This has nothing to do with a critique of evolution. Evolution is the process by which descent with modification produces different organisms from a common lineage. We have extremely detailed natural explanations for the manner in which this occurs, and this includes for the human body as well as other organisms and devices found in biology. "It is so complex" is not an argument against evolution since evolution is not a chance process and by definition can and does produce extremely complex structures. As the geneticist James Watson put it "evolution is smarter than you are". You are obvious unfamiliar with evolution yet for some reason think yourself an authority on the matter. You are not. You are ignorant. When you are versed in molecular, developmental, microbial and anatomical biology, as well as genetics and evolutionary biology, you can make an informed judgement on whether the theory of evolution is sufficient to explain the human body and other organisms (it is). Until then, you are simply making an argument from your own ignorance and concomitant argument from incredulity.

Let me demonstrate to you your own ignorance:

Give me the single sentence, working scientific definition of evolution employed in biology. Do not use Wikipedia.

Exactly. You cannot. Since you cannot, you know absolutely nothing about that which you are meant to be critiquing.  Now, you can come back grovelling, apologize for your own ignorance, and I will tell you the exact definition.

How do you know that? Are you a trained physicist or cosmologist? You haven't even defined the Big Bang. I shall ask you the same question (which again, I know the answer to): Do you know the working scientific definition of the Big Bang, in one sentence, used by Cosmologists? You haven't justified your assertion pertaining to the chance or lack therof of the BB occuring. You do not even know what BB theory says. Hence, you cannot argue against it because you don't even know what you are arguing against. You are not versed in BB theory. You should not comment on that which your knowledge is nonexistent. You should not display the Dunning-Kruger Effect. In fact, unless you are knowledgeable on the subject, you shouldn't really pretend you are. In short, stop talking.