Confusion can arise because you have to understand the limitations your tools are putting on you and how that carries over into JSBsim and understand the limitations JSBsim then puts on you.
The real world is a fine thing, but you're not mimicking the real work, you're simulating it, so some flexibility has to occur, let me explain.
Using a Clark Y airfoil, designed in 1922 for a wooden prop to model a 2022 composite prop by rotating the blade to match those values found in 'the book' will deliver a prop that wont do the job.
Frankly javaprop will never model the propeller you're after correct, it simply doesn't have the airfoils. So you're going to have to make a prop using it that delivers the correct thrust for power but won't have the correct blade angle.
My advise, learn how to use javaprop correctly and understand the data it's outputting and it's limitations.