Actually, when it comes to Science a "theory" is not a theory unless there is a lot of testing and predictions that turn out positive. There has to be a lot of evidence for something to be considered a theory.
Chi has none, no evidence that has been successfully demonstrated in a controlled environment.
"Proof", well absolute proof is not epistomologically possible, however, that does not mean that it has a ton of supporting evidence behind it. In addition a "theory" has to make predictions beyond what has already been observed, if they turn out to be true that is good support that the theory is true
Example - Einsteins theory's meant that light would be effected by Gravity, something not believed before that. It was tested and he was right, this lends support to the theory.