Vayne would play the game from the base, meaning she'd never get killed, but last hitting would be almost impossible at that distance, since the projectiles would take forever to get there
Not at all. You'd just target minions before they started to get focused. And if you could get wards in the lanes behind the last standing tower, you could farm before the minion lines even met.
It is global, but heals enemies every time silver bolts activate, including minions.
Are you happy now ?
Okay, so she won't put any points in Silver Bolts anymore. --- "That is why war is so tragic. To win means to make victims of your opponents and give birth to hatred." - Kratos Aurion, Tales of Symphonia