In the last 5 years, he's beat Dantonio three times ('09,'10,'13), JoePa (if you still call him a top coach, I don't) twice ('09, '10), beat Gary Pinkel once ('10) and beat Paul Johnson once ('09). In the three times Iowa has played OSU in the last 5 years, Iowa has lost all 3. Overall he is 1-8 vs. the Buckeyes. Losses to Stoops and Miles in the only times he's faced them in the last 5 years.
I don't know. I watch the Hawkeyes a lot and I don't think Ferentz still has anything left in the tank. Nor do I think he'll leave Iowa, but that's a different question.