The waiting is *sooo* hard when you're worried about medical tests. I don't have any good answers, but I do know that it helps me to realize that I'm taking all the right steps toward finding out what's wrong and then treating it.
You and Jonathan are doing the same thing: you've been to the doctor, gotten the right tests done, and you're ready to follow up with whatever you find out needs to be done next. Remember that the headaches can definitely be from just about anything, and you two are certainly going through a tough time right now. I don't know anything about twitches, but there are also harmless explanations for those as well.
A friend and I were discussing health anxiety tonight and realized that what makes it so obnoxious is that immediate mental jump to whatever the worst-case health scenario is. For instance, I get a little rash in the rash and what happens? Do I think, "Oh, that's odd. Huh. I guess it'll just go away like it came."? Noooo, I have to immediately think it indicates an allergy to *water*, for crying out loud, and that my throat will close tight any minute and I'll die before help gets here. Mind you, I've never been allergic to anything in my life, let alone water.
So what I'm saying is, those of us who fight health anxiety almost always jump to the worst, most frightening outcome possible, when all chances are that everything is just fine. Having something different or weird about your body - or Jonathan's - doesn't mean it's something lethal.
Remember, you're both doing all the right things to take care of his health, and that's something to take a little comfort from.