You have a number of problems as follows.
1: Your character is not in zero world space, its off on the x axis by -0.415 cm, not ideal at all. When you make a character you want to set the pivot point at its feet using the Axis Centre tools at -100 on the y axis. then zero out the x.y.z. Optimize the mesh to make sure there are no floating points. Next freeze the mesh position. The scale of character should be right also. Then start to add the rig.
2: while the right arm is not weighted as well as the left the topology is not optimal, The characters top seems to have too many polygons, while the articulation points on the elbow have too few and are triangulated for some reason, either way it will still bend but a extra loop either side of the elbow and wrists articulation will help.
3: You didnt rig with symmetry on, plus the whole rig is off x axis because your model was also. You dont always need symmetry on, but when your models limbs are symmetrical it makes it easier. The Clavicle joint position for the shoulder should be in line with the arm pit, as its not the arm pit area will have bad deformation. The Elbow joint position is not located at where there is a loop. Plus you need at least one loop either side of the articulation loop to hold the form of the mesh better. Same for wrists. There is enough loops for knee, if not too many compared to the too few on the arms. There should be a more consistent polygon distribution throughout the mesh. If your aim is low polygon then you need fewer for legs and torso and dreadlocks also unless you need extra detail there. If you want to triangulated then why are some mesh parts not, and why triangulate it at all, you loose your ability to add extra loops or modify the model? Unless your intending of simulating the torso clothes there is no need to have a body under them, its more polygons not needed, and more intersecting issues you dont need when weighting.
Once you put the mesh in zero world space, put the joints in abetter position, add a few more loops your see the arms with auto weight much better, iv tried this by doing the above, removing the weight tag and rebinding it again. Your get away with the mesh just about, but its not ideal, hope you have the non triangulated version still?