Then scientists plugged infinity into the model, which is not "a range of input values", and what popped out? Black holes, big bangs, heat death, an endlessly

Then scientists plugged infinity into the model, which is not "a range of input values", and what popped out? Black holes, big bangs, heat death, an endlessly expanding universe. Without infinity, cosmology as you believe it is cooked. Infinity is just a way of pretending it's not a closed system. Anything is possible in an infinitely open system.