Obviously most DKs love killing and torture when they are doing it, but does Tev ever feel remorse for doing it? Or is he in full control and genuinely enjoys it?

Tevruden genuinely enjoys murdering people, and usually doesn’t feel remorse. He generally limits himself to ‘acceptable targets’, whichever enemy the horde has itself pointed at at the moment. Given that everything he kills is ‘socially acceptable’, and the mindset of most of the Horde on killing your enemies, it allows him to basically go out and kill things whenever he wants; losing control is not typically a problem.