I have not seen so much Drivel and conjecture Written about adsense PSA ads
Simple rules for Adsense
1/ Make it easy for google to find Relevant Keywords
a. Your Ad placement has little do with PSA's being Served
b. Your site has Lots of JavaScript at the beginning of the HTML code making it hard for google to determine relevant Keywords
c. Add Google Targeting Tags around the Posts to Tell googleBot where to look for Keywords.
<!-- google_ad_section_start -->
<!-- google_ad_section_end -->
2/ Give Google enough time to Serve Relevant Ads
a. If Keywords are common and ads are available ,relevant ads will be served in minutes ,not hours ,not DAYS.
b. If There is very few ads for the available keywords ,PSA ads may continue to be served , Maybe time to change the Keywords.
All of the above Advice and more is available on the Google adsense Help pages