How did you create the ad? Via adsense? or via feedburner?
To your second question, I just added adsense myself last week. I added just one block of adsense, the big ugly one right below the post title. That is suppose to perform best. Here are some tips that helped me.
I didn't want the ad to be displayed to my subscribers, so I use whydowork adsense plugin to display ads in posts that are more than a week old. That way my subscribers can read the post without any ads, it gives them a week to read my post. After that everyone sees the ad. I figured this was a fair compromise. Adsense optimizer plugin does the same thing as well.
Here is a heat map of ideal placing of ads
https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=17954
Experienced bloggers might be able to add more as well. If you have any questions, give me a shout out.