No Von Mises Flexural Moment gets extracted since it's not a direct output given by ETABS.
It could be possibly computed within the BHoM in case it's required.

The Von Mises Moment is not returned by ETABS natively and it must be computed directly in the BHoM from the Von Mises stresses diagram.

Thickness of panels is extracted differently depending on the type of deck/slab/wall section property assigned to the panel.
The ETABS API provides different functions for each of their types and they must be all called somehow until the correct one gets hit.
The control parameter is the integer ouput ret of the ETABS API functions (0=Worked Fine, 1=Failed)