My guy I don't mean to rain on your parade or be disrespectful in any way but this is how hardcore followers of other religions feel as well. Faith and beliefs do not make something truth.
Humans believed for 1000s of years that the earth was the center of the universe and that sun gods and moon gods controlled the cycle of day and night when in reality the earth itself orbits the sun and the rotation of the planet determines whether it is day or night for you. There's numerous examples of humans believing things that are untrue to explain phenomenon that they don't understand.
You can say you believe something is the truth that's a hypothesis but claiming it is irrefutable or absolute truth is foolish. Probability wise one group has to be wrong. Hubris, fear, and our own cultural biases prevent many from believing it might quite possibly be their group. You are right about one thing the hypothesis here about the afterlife is truly only testable in death but dead men tell no tales so