The "scale of tentativity" you are asking for is the evidence, Faith.
There is greater or lesser support for all scientific theories, so they are held and accepted by scientists with greater or lesser levels of tentativity.
That's why, if you want to discuss specific scientific claims,
you need to do your homework and make the effort to educate yourself on what is known and not known.
Science, as I have said, deals in probabilities, not certainties. So, there is a sliding scale of tentativity, with things like common descent, the Earth orbiting the sun, and that matter is made of atoms being of very high probability and of low tentativity.
In addition, like I have said, it seems clear to me that you would benefit from aquainting yourself with the tenets of science.
Here are some good places to start. And please don't just reject them out of hand. Even if you do not accept the conclusions of science, at least make an effort to understand the scientific process.
short explanation of what science is