How do I make big decisions when the future is uncertain?

You are being asked to choose a direction when no one can promise you where it leads. That is not a flaw in you or the situation. It is simply what leadership under uncertainty looks like. Everyone who has ever set a course did it without seeing the end of the road. Conviction and humility are not opposites here. You can commit fully to a decision while still knowing you might be wrong. The bet is yours to own, and owning it plainly is what earns people's trust, more than being right every time. What you control is the quality of your thinking and your willingness to adjust when the facts change. So make the call, and say clearly that it is your call. Then write down what you expect to happen and why. When the future arrives, you will have something honest to learn from, and the next decision will be a little wiser than this one.