Does draven have the highest dmg among all adcs ?

No, having high crits is not everything(except for jhin). Most adcs outdamage him in the late game. has much higher crits and actual dmg abilities, outdamage him hard due to having much more sustained damage and in the late game they have big crits too except kog, have aoe dmg and twitch q as steroid combined with ghostblade makes him do ridicilous amount of damage + it's easier for him to get it off instakill everything in their sights late game.Vayne also has super high crits late game with q, which is close to dravens crits or even bigger.

However he outdamages pretty much everyone in the mid game if he gets few kills

Played perfectly, I believe Draven and Vayne have the best dps, though who gets the top spot varies based on enemy armor and health (high values of either tilt the balance in favor of Vayne for obvious reasons).

single target. yes he can 2 auto people.