Is there any way to change a setting in the game to automatically sell items to a vendor one at a time without having to continually hit the amount slider first? I have 133 items I pilfered and I'd like to get the "speech" credit for selling them off.

Assuming of course that you don't get a 1x133 towards speech if you sell them in one bulk as it defaults meaning it would cost me a potential of 132 speech points.

No.