Hey man, I see a few problems with your rig. When rigging, you ALWAYS want to attach pegs to your individual drawings. Pegs “separate” the Transformation data from the drawings, which makes it so you can scale, rotate and move the drawing (on the peg layer) without actually “Destroying” the drawing, it basically makes it a non-destructive workflow.
A good thumb rule when rigging is: Never have a drawing control a peg (meaning, never attach a peg to the bottom of a drawing node) Always go peg to peg (with exceptions of course. But the drawing rule always stands)
Based on your screenshot try doing this:
Delete everything except the two drawings and the composite stuff. attach a peg to both of them. (before you do, go to edit->Preferences->General-> under the “Settings” section, enable “default Separate Position for Pegs”. It’s a technical thing, but in short, it separates your X,Y,Z Data out into their own separate layers as a default.)
Go back to Node View, Select your upper arm Drawing layer, create your deformer (remember to put on the envelope deformer, even though it’s just two points, long story short, it makes your rig easier to animate)
When the deformer is done there should be a deformation group between your upper arm drawing and peg.
Now create your kinematic output node, attach it to the bottom of the deformation group, and attach the hand peg to the bottom of the kinematic output.
The upper arm drawing should just go directly into the deformation group.
Done, you can now deform your arm and the hand will follow. set up your pegs Pivot points and you have a working arm. 
Basically the kinematic output, is used when you want something to move with a deformer without it “deforming”.
play around and try and detach the kinematic output and put the hand directly into the deformer. you’ll see what I’m talking about
Hope that helps a little. Hang in there. Rigging is fun, but it’s a bit of a steep learning curve.
