I'll try and answer your questions:

1. Minimal Usually to lateral to another federal agency but only if you have a college degree.
2. Varies. Currently not hiring but usually 6 months to 1 1/2 years.
3. Never. You only move if you want to and after 3 years at your initial assignment and at your own expense. To promote to GS13, but at your own expexse. To promote to GS14 is a paid move.
4. Witness Security, Investigative Operations (Regional Task Forces), Judicial Security (Judges & Facilities), Protective Operations (Deputy Attorney General & Drug Czar), Special Operations (Tactical), Assett Forfiture (Seized Assets).
5. Yes
6. NO
7. NO. Try a recruiting officer from another district but they will currently tell you to keep checking the website. Hiring process is currently being revamped. Nothing in the works until next year.