You are absolutely correct regarding the Nancy Hanks issue. What also bedeviled some was Nancy singing a song to Abraham that hadn't been written yet. I have to believe that didn't really bother Sandburg much because he was going for a scene in The Prairie Years rather than writing a monograph.
As for the books, in my article in the Journal of Illinois History on Sandburg and Randall, I compared the publishing history of The Prairie Years to Randall's Constitutional Problems Under Lincoln. Randall had to pay to get his book published, and it never (as far as I can tell) sold out. Sandburg sold 48,000 copies in the first year alone. Yeah, I agree that there was some jealousy there.
Best
Rob
Abraham Lincoln is the only man, dead or alive, with whom I could have spent five years without one hour of boredom.
--Ida M. Tarbell
I want the respect of intelligent men, but I will choose for myself the intelligent.