Belief and Knowledge

[Neo-Scholastic]

Bullshit! If you have any opinion about how the world works, either 1) with divine influence or 2) without divine influence, then you have a "worldview." And that worldview does affect other beliefs, like what you believe about religion.

Would you then argue that theism based on the standard definition, which includes multiple religions and doctrines, is a worldview?

Yes and it would be option 1). That option does not conflict with various religions having different opinions of how or who is exercising divine influence.

it is possible to believe that there isn't a god now, but there was one in the past.

To my mind that falls into the category of option 1. A divine influence in the past (or future) is divine influence still.