Lee,
As many have already suggested, your best course of action is to send the blade to Bob B. The state it's in, you'd have to get it polished before you send it to shinsa. I'd actually be more worried about the broken kissaki than the authenticity of the mei. Bob can help with that too. Judging by the position of the yokote, it looks like 3/4 of the kissaki would be lost if repaired. Loss of boshi would make most swords worthless.
What I do know about kiyomaro, is that he didn't favor horimono. So it may not be original. From what I see, the futatsugi hi looks well done but the ken doesn't.
Also consider that kiyomaro was famous in his own time (thus fake blades were produced even while he was alive.) After the wearing of blades was banned, demand dwindled almost overnight. The only blades people wanted were ones by famous smiths so even honest tosho like Gassan Sadakazu were making gimei blades. You'll find that many gimei blades of various quality were produced during this time.
This is why we all might seem a bit critical/skeptical. Minomoto Kiyomaro is just about as big as it gets.
Best of luck with the blade!
mike