Q1. When one pack is inoperative, the other pack runs at a higher flow to compensate - this creates a higher demand for bleed hair from one of the engines.
RTOW calculations assume an engine failure at V1 - continue - and meet the minimum climb requirements. In the example above, the most critical engine failure would be the failure of the engine with the pack inop (for example - L. Pack inop, Left engine failure is most critical). Now the remaining engine needs to provide enough thrust to meet the minimum climb gradient, AND provide higher than normal bleed supply for the operating pack.
This is why there is a weight penalty. (Although I agree, intuitively, a failed pack should translate into a lower bleed demand and more thrust being available). You have to remember that the RTOW is for the more critical engine failure.