adding to 3) As far as I know, no daedra has a human life cycle. If they die, they are stuck in the cold blackness of Oblivion till their master releases them. I'm pretty sure they keep their form. Also, I believe they do have reproductive organs, but not for popping out babies. I bet they can lust, love, etc, we just don't see, hear, or really know about it, and the majority of intelligent daedra won't just go and have an orgy or get it on. Though, from what I gather from Battlespire, they still can love and have a very deep connection to each other.
Here's a good quote about some nature of daedra
Sinder Velvin: I don't know exactly how to break this to you, but -- Well -- Maybe you have better take a look at this dagger. She said -- Deyanira -- That is --
Jaciel Morgen: Aaaaaa! She is gone! GONE! I should tear your beating heart out and force you to eat it in tiny bites, one wriggling, beating bite each century! I should flay the skin from your body and hurl your living carcass into the sea of my salty tears.
Sinder Velvin: She did it for you.
Jaciel Morgen: You, mortal -- No doom so slow, no pain so tearing --
Sinder Velvin: Nothing you do will bring her back. She'll be back in her own sweet time, from what I understand about you Daedra. And for all that sweet time you can think about how little you cared for her, and how lonely you'll be without her, and how much she was willing to do for you, when you wouldn't do anything but pout and snivel.
Jaciel Morgen: What you say -- Perhaps is true. Too fair. But... You BASTARD! You TRICKED her into this, to serve your own SELFISH ends!
Sinder Velvin: No. It was her idea. I haven't got her kind of vision. Or character. I admit. I'd lie like a rug to save my skin. But I haven't got the imagination to think of a thing like she did. And it would NEVER occur to me that she might do it of her own free will. In fact, I'm sorry. And ashamed. That I helped her to do this thing.
Jaciel Morgen: Perhaps I can understand. You are a mortal. And mortals see things differently. A mortal must never regret, never feel shame, for what it does to save its life.
Sinder Velvin: Normally I'd agree with you wholeheartedly. But that's not how I feel right now. Look. She isn't really dead, is she?
Jaciel Morgen: Daedra do not really die. Not as you know death. But we can sacrifice ourselves to Oblivion. As she did. Oblivion is existence and self-awareness without the ability to see, hear, or affect the world. For an immortal it is hell -- Unspeakable pain and horror -- Absolute loss. Eventually we do return. But not all return as they were. There is sickness. Madness. Change.
Sinder Velvin: I'm sorry. I hope Deyanira will be all right. She certainly has a strong spirit, if that's of any consequence.
Jaciel Morgen: It is passing strange, but I feel your comfort, mortal. You have so much to lose, you things of flesh, and yet you do not despair. An intriguing mystery.
Sinder Velvin: Yes. My flesh does have a lot to lose. And another, a close friend, is also in danger. So please help me. How may I leave this place?
5) Around the time of the creation of Nirn
6) No. Only the daedra, your butler, and that one order guy. However, you are now the new Sheogorath and will mold into him completely in time. It would have been like he never left.