1. Will my TD status affect my TN application?
No.
2. On the Employer letter, should I put my current address in US or my address in Canada on the letter? My concern is if I put my current address on the letter, it could be rejected because of immigration concern.
Should have no your address on the letter which you will show it to immigration officer. Should have something like this:
Immigration and Naturalization Service
Treaty Officer
U. S. - Canada Port of Entry
3.Comparing preparing all the document by myself with getting help from a attorney, which one is safer?
You can do it by yourself
4.Would the officer be reluctant to issue a TN to a Canadian?
No