1. I don't know; I haven't done any of the civil war.
2. I'm not sure, other than the obvious things: the channeled one will dual cast if you just press both mouse buttons, and the single cast requires you to release both mouse buttons at once in order to dual cast (after charging the spell, of course).
3. 110% faster means that the amount of healing, or HPS (healing per second) is increased by 110% for channeled spells, and single cast spells will heal 110% more HP. I think you have the right idea for the magicka costs.
2. I'm not sure, other than the obvious things: the channeled one will dual cast if you just press both mouse buttons, and the single cast requires you to release both mouse buttons at once in order to dual cast (after charging the spell, of course).
3. 110% faster means that the amount of healing, or HPS (healing per second) is increased by 110% for channeled spells, and single cast spells will heal 110% more HP. I think you have the right idea for the magicka costs.

"Spells cannot be mapped to Right Hand."
Yes they can.
I just tested with spells in my right hand and a Shield in my left hand. Is that what you meant? In my current game, I'm always dual-casting augmented Firebolt but in the Pacifist game, I want to have a shield in my left hand to ward off arrows and hits and a Calm, Fear, Paralyze or Heal spell in my right hand.

Yes they can.



Yes, that is what I meant. How do you do it? Are you on PC?