Is the text mentioned in the history of Tabari regarding the Umarian Covenant the most correct, or is it the text that other fatwas have relied upon?

There is a difference between the Umarian conditions and the Umarian covenant. The Umarian conditions are established in Musnad Ahmad and history books, and Ibn al-Qayyim discussed them in "Ahkam Ahl al-Dhimma". As for the Umarian covenant you mentioned from Tabari's history, it is specific to the people of ash-Sham.