You might find this link helpful. I found it after google-ing "Sir James Abercrombie" after we found papers tracing my grandmother's family through Alfred Franklin Sims to Colvill Abercrombie to Sir James Abercrombie. But b/c some of the dates looked off, i kept digging and then came across your post here. Very Helpful! your research helped me see that my family had skipped Sir James Jr and went straight to Sir James Sr.
I have just started searching and haven't been able to authenticate much, but hoping it's all true!:)