Leo Donofrio has addressed all of your points. If you take the time to read his legal opinion, you find answers to the issues you pose. His blog is at http://naturalborncitizen.wordpress.com
He advanced this theory well before the “born in Kenya” mess became popular theory. He also applies his theory to McCain and not just Obama. He provides plenty of present day examples. I won’t try to summarize as I wouldn’t do his arguments justice.
No, he didn't.
Leo Donofrio jumped onboard the birther bandwagon right at the end of October 2008, when he filed Donofrio v Wells. The "born in Kenya mess" was introduced in March 2008 to no interest, finally caught the web's attention in June 2008, and got widespread attention with Phil Berg's complaint in August 2008.
So the Kenyan-birth eligibility accusations had been circulating for at least four months before Donofrio started advancing any alternative theories as to Obama's ineligibility.
Rather, his case against Obama was premised on the argument that Obama might have been born overseas and that the New Jersey SoS hadn't conducted any independent verification of a Hawaiian birth. Nothing about his father's citizenship being a disqualifying factor in-and-of itself.