1. I guess it are still the same ones you submitted to "back in the days". There are some newer ones that are certainly worth submitting to.
2. Sponsor content gets accepted by most LL's as you probably know and converts better indeed. But some of the content out there is already way overused so that's always something to look out for.
3. One link back is acceptable but counts as 1 of the 3 outbound links allowed.
4. I am (
http://www.smilingpussylinks.com)
5. Why are you asking all these questions? You run on eof the biggest LL's out there