Long Tail Keywords, Micro Blogs & CPA Offers

I am thinking of making 3-4 micro blogs targeting long tail keywords and adding few cpa offers.

Health
Insurance
Credit Repair

are the niches that i have decided to work on.

Now The idea is to find decent traffic low competition long tail keywords and expect my blog to show up for these keywords as the competition would be less for exact keywords.

I did a test with auto insurance keyword around 4-5 months back, the keyword had around 200 searches per day, competition of about 2000 for exact match and it got ranked no: 2 within 5-6 days.

i had .info domain with it and left the blog and today its on page 2. So i am confident that if done right its possibel to build up a sizable traffic as you start making these blogs and keep tweaking and updating it.

Ok, here are the questions:

1- Should i go for a proper domain name or will it work equally good with a wordpress domain?

2- Any suggestion regarding finding Long tail keywords, any good keyword tool you can think of. I am currently using wordtracker and love it.

3- A resource where i can find high PR networking sites , i have a big list but i wana know what is presently loved by google.

Any suggestions would be of great value to me. I am not a newbie neither a guru. An average marketer . Have learned few tricks of the trade only by myself.

So please pour in your suggestions, that will be of great help to me and inspiration as well.