Hate to be picky, but:
2) Equating potential energy at ToD with energy burn during descent (Drag x speed)
Force x Speed = power (not energy)
You need more drag to dissipatethe greater PE, so it has to act for a longer period
Force x Distance = Energy transferred (i.e. work done)
Talking about a "longer period" implies you mean time; if you are talking about forces and time you are into the realms of accounting for momentum, not energy.
If there is greater PE, then Force X Distance needs to increase in order to get rid of it. So you can have more drag for the same distance (the best L/D scenario), or the same drag for a greater distance, or some other combination (e.g. a little bit more drag for a greater distance; the 'high speed descent' scenario).
pb