So I did my rear brakes, all seems well except for some major rubbing between the drum and backing plate. What can I do to fix that?

 

i would just bend the backing plate very gently away from the drum, ive had this happen to mine several times where the backing plate has been beat up on rocks and whatnot.

if your backing plate appears to already be straight you might want to check your wheel bearing and axle housing to make sure they are in good condition