If you "think" you might be using too much weight then you are. Form comes first always. As far as movements for the back
Pullup(or chin ups or Pulldowns if your too weak for pullups)
As far as biceps I know it seems like a no brainer but make sure your keeping the arms tight and squeezing at the top. Sometimes alot of people just toss the weight up and down with crappy form.
my favorite bicep exercises on top of regular DB and BB curls!
Incline bicep curls
Gironda Perfect Curl
Reverse Preacher Curls