For the 512 pedal assist, how many levels of assist are there? Also, how much pedal assist does each level provide? Exactly how much power? Is it 100% per level? Is it more or less?

There are 5 different levels of pedal assist and each level will add additional power. You can basically customize the power of each assist level of PAS and throttle power respectively via the Smart Motor App. The percentage of power will increase by each level.