Bible - confirmed by science, page-19

If (evolution) that cannot be reproduced under controlled conditions what basis is there to believe it happened in the past? All that has ever been proven is that creatures can only reproduce ''according to their kinds''. Examples of successful mating of creatures of different kinds are nowhere to be found.

This is not entirely accurate, as I suspect you know, but setting that aside for now neither can Watchtower's "theories" be reproduced under controlled conditions. The creation of Adam and Eve's from dust or whatever and a rib respectively, nevermind the creation of the universe have never been repeated under controlled conditions so using your criteria you need to reject the Watchtower "theories".

Confidence is scientific theories comes from observable, verifiable facts that match the theories rather than in our ability to reproduce them under controlled conditions.

In the case of The Theory of Evolution, these verifiable facts come from genetics, biology, geology, palaeontology etc.

In the case of gravity, we can't even reproduce it even to a limited extent as we can with living organisms but have confidence in the theories of gravity from the observable consequences of the theories.