Is this really accusative? Could I say "nu îţi cred"? If so, what would it mean?
You can't just say "nu îți cred". You can however say something like "nu îți cred minciunile" meaning "I don't believe your lies".
could you a 'pe tine' to the end of the sentence without changing the meaning?
Would not adding "pe tine" be "pleonastic"? But, apparently not as seen in the next presented sentence: Andrew is following you.
Can this be translated as "I do not trust you"? And if not, how would you say "I do not trust you" in Romanian? Multumesc :)