Concerning your first question - the extent of Einsatzkommando Tunis' actions and evidence for it:

The rules governing their actions were effectively identical to the rules for the Einsatzgruppen in the Soviet Union [p. 138, Mallman and Cüppers][1].

There was a meeting between Rauff and the Wehrmacht where they agreed to use Jewish forced laborers to fortify the frontlines [p. 204, Mallman and Cüppers][1]. The source quoted for this is the war diary of Pz. AOK 5, which wasn't Rommels general staff.  

Einsatzkommando Tunis stayed in Northern Africa for about 5 months. During that time "they were mainly busy registering Jews, exploiting them, terrorize them, and force them to comprehensive forced labor for the Axis powers. Even if mass murder did not happen, Rauff and the rest of the German occupation hierarchy set up a true reign of terror" [p. 207, Mallman and Cüppers][1].

I found no mention of more than 2500 deaths in slave labor camps.

With regards to your other question - Rommels alleged promise to cooperate:

That accusation is probably false. Rommel and Rauff most likely didn't meet personally, since during Rauffs visit to Tobruk in July 1942 Rommel was leading his troops in the decisive phase of the First Battle of El Alamein, 500 kilometers to the east of Tobruk. Rauff probably put himself under the command of one of the staff officers of Panzerarmee Afrika (PzAA). There is no conversation note however, reason could be a priority in reports about the combat at El Alamein. Possibly important staff intelligence and quartermaster documents of PzAA from those days are missing. [p. 138, Mallman and Cüppers][1]


  [1]: http://www.amazon.de/gp/product/3534197291?*Version*=1&*entries*=0