This can go on and on....Let's cut to the chase...I agree that the original historical accounts of life of Bahaullah for the most part are in Iranian Language. With some exceptions of the books that E.G. Brown had written on the history of early Babi and Bahais. However, those original historical accounts of life of Bahaullah also for the most part are already translated into English. Now, specially if we are limiting our investigation to evidences of Bahaullah's education and human learnings, the matter from my experience does not require an extensive investigation in all subjects.
Specially, even those who tried to refute Bahaullah's claim, have provided translations of anything that possibly they thought they could use to refute Bahaullah.
Sure, but how much all these are required also depends on the time of events. For example if we want to know about the life of a Person who lived 2000 years ago, constructing history and writing it up, would be much more difficult than, if we are investigating into life of a person who lived 150 years ago, and specially when we are only now in this thread interested in how much Bahaullah had education or learning.
Do you have credible scholars of history who have written reasonably well acclaimed life of Bahaiullah (like historians have done for Churchill or Gandhi)? If yes, share the link. If not, I am not interested as I cannot verify or refute the sources and their authenticity/accuracy myself.