See if my pictures are of any help. 
Fan should just pull off after you remove the six bolts. The shaft is straight and has a woodruff key. I showed a safe way to pull with a bar puller so no hammering is necessary. They also sandwich up to the driving hub and hold pulley assembly. 

Thank you for help, another member gave me video of The Pacific Northwest Hillbilly (Matt) taking a 1950 D4 7U water pump apart and followed with reconditioning. I have watched most all of his repair videos. I missed the water pump repair video. I am so glad I became a member Acmoc.

I just went back and reread your original post.
I sorta missed your question.
You need to remove the broken bolt on the adjuster.
Looking at this one I see that this has a broken bolt. But you may still have a second one like this one.
If you can drill the broken bolt centered, try an easy out.
May take some heat from an acetylene torch.
Since I have a milling machine I can accurately drill it.
If you can’t drill it yourself or mess up the thread you could try drilling it for a 5/16” bolt.

here a tip clean the dirt off it and soak with your favourite brand of possum piss. and the big secret is allow the time for it to soak in re-apply a couple of times too. impatience has broken many things.

a soldering iron can be handy for applying heat to thins like screws and small bolts and being precise with the heat unlike a heating torch.