As my associate Stnylan has covered the concerns on characterisation and offence, I shall merely nod in agreement and devote my attention to the other areas you invited comment upon.
In terms of plot I would expect the post-Longstreet election to be interesting, so I have applied my intellect to the question and consulted Wikipedia to augment my less than impressive grasp of civil war era America.
Thus far the CSA has gone for ex-military Presidents (Davis then Longstreet), if they do it a third time then that starts to be a tradition. I would therefore expect an ex-General to give it a go (say Richard Taylor or E P Alexander who both look military competent and well grounded realists), running as Longbridge Part II on broadly similar policies, maybe after a bit of arm-twisting "Don't abandon the nation!", that sort of thing. I can also see some regular politician going for it, say CSA Vice-President AH Stephens, running as a 'The confederacy is a normal country so should have normal, political presidents'. To mix it up it could be interesting to see Beauregard go for it, he ticks most of the boxes (civilian before the war, excellent war record, smart) but his attitude on slavery could ruin it for him. As the Patton's have been set up, if one of that dynasty has a 'good' war they could be a candidate, but I expect the older generation of Civil War veterans to be first in line, maybe a Patton as a VP for a 'political' candidate to balance the ticket?
Coming now to your last comments, you can rest assured I wouldn't be bothering to comment here, let along look up old CSA generals, if I wasn't enjoying reading this. One of the few bad effects of improving your writing skills is that it makes your early efforts look less assured, it's a problem I've had myself, but it is a nice problem to have. If you want to change something then go for it, but there is nothing in particular I think needs to be changed.