He's trying to stay alive, is what. As for FBI coming down on him harder: it would probably be better for him if they would allow him his day in court. There's a whole lot more that has gone down here that has NOT made the papers, or the press conferences, but will likely be brought up by his lawyers.
For now, I think, his best chance of not ending like the other couple dozen microbiologists who have died in the last few months, is to stay right up front in the public eye.
Oh, and the blood test. He obviously wants that done, and if he's suspicious of what the FBI is up to (as am I at this point) it stands to reason that he would want an audit trail of both the test AND the methodology. That would help establish if a test was good, botched with a wrong method or errors in procedure, or deliberately crashed. Remember that he is, himself, competent to sign off on the methodology log.
I understand that--and but I'd bet that he's probably already had a blood test, an interpretation of the results, either by the lab or by Hatfill himself or both. So why the push to have the blood test done by the FBI lab, except to show that the FBI lab is incompetent.
If my premise is correct, it sounds more like Hatfill is laying the grounds for a criminal defense rather than trying to exonerate himself.