"2) A PC playing an eloquent speaker enters a debate with an NPC eloquent speaker. How do you allow player skill without holding them to being an eloquent speaker themselves?"
Ryan's second question is a good one!
How do we allow the encounter to be decided by skill of the player, rather than skill at oratory?
First, I would like to say that personally in my own games, I try to have as little as possible be a completely subjective judgement. Any judgements that have to be subjective, I prefer to decide by consensus or random die roll.
That said, I think it is important to remember what player skill is. It's your ability to gather information by asking questions and make decisions to survive and succeed at encounters.
This is no different when encountering an NPC. They don't have to use oratory to convince you. They don't have to impress you or be charismatic or smooth.
They have to gather information and make choices.
So how do we do this?
Constructing the NPC
Encounters with NPC's need to be designed. Inside that design there need to be mechanical systems and hooks for resolving conflicts. Then the encounter then becomes again about gathering information and making choices.
For encounters, I generally set a timer based on the reaction roll. Every action during the parley reduces the timer by one step. This means they have to weigh what interactions are most important. Will they spend the whole time asking questions? Will they Threaten (Check Result & Morale modified by situational factors. Apply result to the current reaction roll) or Offer aid and possibly get a quest? Will they joke or drink in order to gain time for more actions? Offer to hire the NPC (only accepts if his reaction is 9 or higher)? (The complete list is forthcoming.)
This means the NPC's are designed with various reactions to these choices. This means the players get a chance to explore an NPC. They gather information by asking questions about what the NPC looks like and how he responds, then they make choices. Their ability to orate or speak eloquently has absolutely no bearing on the encounter.
This works in city adventures too. Information about other NPC's can be asked. Players can be given quests, end feuds, get swords left at home, and kill rats!
For longer term PC's, they provide literal hooks, like menus, to allow the players to accomplish tasks. Sages will turn gold into answers. Mages will turn gold into identified items and magic goods. Alchemists will turn gold into potions. All will give quests.
For those that travel with the party, long term loyalty and bond relations can be tracked for romance options and in-game benefits.
In all cases it requires a little bit of forethought and design, and then the NPC becomes like any other part of the game. One that becomes a test of player skill, and not something subject to pixel bitching, DM Fiat, or attempts at mind reading.