The first fallacy is that every use of “God willing” necessarily signals doubt about the present. The expression may be used for future events, humility, or qualification of an outcome.
The second fallacy is that every qualification is acceptable regardless of whether the speaker actually doubts the existence of present faith. Genuine assent must remain decisive.
The correct analysis distinguishes context, intention, present and future, and essence and perfection. This is not wordplay: a statement about an uncertain later state is logically different from an uncertain assertion about current conviction.