Actually one way to loosen the stuck shaft would be to heat it up with a torch to cause the outer casing to expand, don’t heat it up to much to cause the shaft and the outer casing to expand together. If you do it this way just be careful.
WD40 is actually a water displacement product that’s what the W D stands for and the 40 is how many times it took to create it. People use it for many many different things. Just a of trivia LOL