Bane's actions, in terms of cutting himself, seem to be motivated by sensory overload. Although he's experienced a range of inputs before, the sheer volume and intensity of the five human senses, especially sound and smell (something he mentioned in the first film as being one of his personal triggers) are simply overwhelming to him.
The film's original script specifically states that his reason for cutting his skin is to give him a single sensation to focus his attention on while he waits for Neo.
Bane sits hidden in the shadowed caves connecting Zion to the dock. He
crouches in an alcove, both arms marked with dozens of knife cuts.
His eyes are animal wide, shifting, blinking, reacting to every sound,
every smell but always returning his attention to the cut as if using
it to focus his thoughts.
Finally, through the tangle of pipes and stalactites, he sees what he
has been waiting for: Neo.
Matrix Reloaded: Script
As to what VDTs are, the simple answer is that we don't know.