At shop to have a chipped brake pad replaced. Mechanic says drum has cracks and should be replaced. I don't know enough about brake drums to know if he is BS ing me or not.
I think the general rule is 2 sets of shoes to 1 set of drums. Those look pretty bad to me, I’d replace.
Those heat cracks probably do not warrant replacement. Drums are marked with a maximum diameter for reuse. Often 16.620 inches ( about 16 and 5/8's ). Does not look like you threw any money away.
You could, so long as it's not on the steer. I wouldn't myself, but on the drive or tandem you likely wouldn't notice that one corner was doing a slightly better job than the others. Up front you'd be wrestling the wheel every time you made anything other than the lightest of brake applications.
Only in a bind. That causes unequal braking. That is a bad thing in the rain. Snow and ice are worse.