Paul Mahwhinney isn't a con-artist, he's delusional. He does not have close to 95% of all the singles released. Any collector of any specific genre who looked at his catalog can tell you that. Also, he might have 3 million singles, but does he have 3 million distinct singles? I know someone who bought a warehouse of 45s, picked through them, and then sold 12 palettes of total garbage to someone for a few thousand and the guy had to haul it away. Don't believe his own hype.
I think for a more realistic estimate on what he has, try posting on waxidermy.com, which is filled with a lot of heavy dealers and collectors (not soul oriented though).