most clerks coming right from law school are JS-11. Usually between 54 and 60K depending on locality pay increases.
Disregard my earlier advice. That sounds right. I do think you can get 70k or more if you have a year or two at a firm first.
Yes you can. The difference is that they are practicing attorney's who are licensed. I believe they can come is as JS-12 or 13 depending on experience.
The only reason anyone is a JS-9 is when your judge says you don't meet the special circumstances to be bumped to JS-11, namely, not in the Top 20% of class, no law review or anything honors oriented. Naturally, the vast majority of federal law clerks easily meet the standard, but I presume there must be occasions where they do not since JS-9 is possible.