2) No, they were not losing money. Both Time on the Cross and subsequent studies (Reconing with Slavery) concluded that slavery was not only profitable in almost all parts of the South, but viable because of the increasing value of property in slaves.
3) My doctoral dissertation was on Southern banking in the antebellum period. The bank loans were as much on slaves per se as they were cotton. (I found the same slaves used as collateral for several loans simultaneously!) Indeed, "King Cotton" proved a bust---Br. and France didn't need it at all.
4) The 40 acres and a mule argument was less about subsisetnce and more about independence. If we had done that, while there would always be a Jesse Jackson, it would be much tougher to ever argue that blacks were "economically discriminated against" after the Civil War, because they would have had basically what most whites in the South had---and, indeed, what most free farmers in the north had.