It's a felony, and jail time is on the table, but if he's smart(he's not), he would cop to it and take a plea for some probation and a fine. Since he's retarded though, and seems to want ride this lie out all the way to the judge, he might be made an example of.
And that's without the whole terrorist letter thing. I'm guessing they plan to use it as leverage for him to just own up to everything. If he doesn't, they could throw that shit at him too. He's basically making the worst decisions possible in this case. Guy is going down in flames, and his lawyers are gonna bleed him dry while he does it.