In my (first) attempt to remove the crank arms from a bike, I broke the crank puller (Super B TB-6485). I applied more force than I was comfortable with, thinking the threads had perhaps rusted over time. When attaching the puller to the crank, I pulled back the driver a fair bit from the coupler, screwed in the coupler, tightened it lightly with a spanner, and then proceeded to turn the driver down as far as I could. I then applied as much pressure as I could, and I heard it snap. Uncoupled everything, and the two bits seen in images 1-3 fell to the ground.
What did I do wrong here? Can the tool be used without the parts that fell out? Should I have removed them beforehand? I'm honestly a little confused as to their function.
Thanks in advance. Images below.