1) If they have wealth, yes. If no, they still aren't eligible for reparations in my book, but it will be hard to get them to pay money/resources they don't possess.
2) If necessary, yes. I'm not sure how you would determine who was more oppressed. Paying them equally is better than no reparations at all.
3) Every other group already got their reparations, including slave owners.
4) Race-based slavery in America. Because, America is the beneficiary of it, and the one paying the debt. Common sense.
Only descendants of slave-owners should bear any burden, if at all, go after them...if there are any left.
That Civil War killed a lot of people before the 20th century...