1. it's them who set a slot to you, not the other way around
2. you come back with a bot to turn it off, but you don't have to in theory
3. Yes it regenerates exactly like rc
4. Yes I would definitely overassign, also keep in mind anyone can contribute to your pool, for instance I would probably delegate 80k worth of rc to your pool so I don't think you will have to worry about the pool running dry.
5. I didn't understand what you mean by "operating an rc pool" but yes you could have a nice pie chart showing how much rc they have and from which sources it comes from
6. yes
7. You can update a delegation to an user at any time to increase/decrease it
8. you can change it every block if you feel like it :)

next example

1. It's per slot, you consume from your first slot and then if there is stll rc to pay it flows to slot 2 then 3
2. yes you can definitely delegate different amount to any user and personalize how much rc each user gets delegated :)
3. it is ! Also removes a lot of burden on pools who would have to fine tune how much they want to delegate otherwise

A. I think the user would probably not need to know about it at all, the idea is to delegate some rc to newcomers until they power some hp up and then they are good to go, that's why the slot 1 is set to the account creator by default, so they can easily create an account and delegate some rc to it at the same time.
B. It's all done at the blockchain level, it's actual rc that is delegated and not some kind of workaround with hive power.
C. See B
D. You can delegate to a maximum of 40 pools but pools can delegate to as many users as they want.