Q1. No, you/your Instructor/your school will arrange with a DPE to do the test, but in the process of doing this, the FSDO is notified and they have the right to insist an FAA Examiner does it.
Although there are a lot of good flight schools all over the US, one advantage I've found of going to Florida in particular, is that there is so much training that you can more easily book a checkride at short notice, because there are a lot of DPEs available. When I thought of doing the CFI whilst on a vacation in LA, the school seemed to find the whole process of organising a CFI checkride a bit difficult. In Florida, this was not a problem. Obvisouly, this is just a tiny sample, but I do get the impression that checkrides elsewhere need a bit of planning to fit into your schedule and that they are available pretty much on-demand in Florida.
The MEI Initial oral isn't a super long oral. It has some MEI-specific content, but omits a lot of content on the various ASEL maneuvers.
The oral is nothing to be scared of. It's all laid out in the excellent "Oral Prep Guides" you can buy from ASA or Jeppesen. Firstly, you should be comfortable with much of it with your background. Secondly, your Instructor won't send you to test unless you are prepared; he will probably do many hours of groundschool to prepare you for the oral. Finally, I've never found a DPE to be anything other than fair - they need to determine that you are at the right standard, but they conduct the test in a way that let's you demonstrate that, not in a way to catch you out.
Q2. Yes, absolutely, the typical way is to do the ASEL CFI Initial. I just mention the MEI Initial, because sometimes people aren't aware of that option.
Q3. Good question and not sure; check FAR/AIM (14 CFR) - it's all available online, as are all the publications you need
14 CFR part 61
Electronic Code of Federal Regulations: Written test guides
Education & Research
In particular, take a look at the FAA Handbooks available here
Aviation
(browse all 3 categories on the left: aircraft, aviation, examiners)
for example the Aviation Instructors Handbook
http://www.faa.gov/library/manuals/a...A-H-8083-9.pdf
The FAA publish for free pretty much all you need to earn all of the FAA qualifications.