How exactly does the statute of limitations work? If you are indicted for a thing and then the trial gets suspended, does that initial indictment not stop the clock, allowing the trial to proceed when it is reopened?
In theory, the President has unilateral authority to declare martial law. In practice, he has to have sufficient support to establish and maintain it. It is not clear that declaring martial law would not result in real blowback and some sort of coup-like action. Government officials pledge an oath to the parchment, not the WH. I mean, the CIA would probably find a way to rendition him if he tried a stunt like that.