I think it's safe to say there were marauders on both sides. The fact that the North was the invader/occupier opens them up to this charge more often strictly by that fact as much as anything. Aside from the border states where this stuff was commonplace, I believe there is evidence that most field commanders dealt harshly with such offenses. Sherman's march and his total war in my homestate of Mississippi probably pushed the envelope more than most. His desire was to break the will of the Southerners....whether he did or not is something we can all debate forever.
No, I think that's been settled pretty well. If the Southern will hadn't been broken, we'd have seen evidence to that effect. To my knowledge there were no Reconstruction-era insurrections (at least, none of any significance) by Southerners, and the secessionist states did eventually come rather meekly back into the Union.
Sherman obviously failed -- though not for lack of effort.