Bananamancer answers 1 and 2 good enough :D

#3 Though sw is hard. Theres no hardened fast values that people have generated because its literally the hardest thing to track. Land/NW/+damage/tpa sent SHOULD all factor in. With that said if it works similar to ET then gains would be ~18% of current mana. That is you'd take 100%->82%->68->55.....12->10->9

In my experience when my kd was using hertics due to 0 offensive tpa losses we would routinely spam ~ 2 tpa "tickly" on a mystic and limit their casting to a couple every now and again..i know how precise. So if i had to guess i would say the range your looking at is likely 2 tpa =5% up to a likely cap of something like 6 tpa =25%