Timing Chain-moving the Crank
In my opinion cam sprockets (they are not gears in this case) should be replaced in sets with the chain. I've replaced "just chains" on DD back in the day, but never on anything performance, or unless it's a used used "junker" that "just runs"
'N yeh. What you have there is a sprocket for advance/ retard use. They normally have three symbols, one for each keyway. Round for "stock" square for one setting, and triangle for the third. The corrosponding mark will be on the matching keyway, which will be somewhere around 1 O'clock when "right."
So far as moving the crank, just MOVE it. The timing marks only align at one point. Sometimes you have to "juggle" the crank a bit to align it. I ALWAYS use a straightedge to make darn sure my old eyes are not "crossed" LOL