(edit: replaced punishment with detainment, it's probably more neutral)
Yes, probably. I'm not really convinced that this isn't a violation of the fifth amendment, but I'm not a lawyer.
I suspect a jury would find him guilty anyway, and the fact that he refuses to decrypt his hard drive will likely not help his chances of convincing a jury that he's innocent.
(Subtextually, I'm saying: the punishment isn't infinite.)
He's in possession of data deemed contraband, but apparently not linked to distribution. The police need to demonstrate possession and can do so when their search is complete.
The police did an investigation, obtained a warrant to search for the contraband and seized the hard drive. The defendant was ordered by the judge to decrypt the drive per the warrant, and refused to follow the order. He's in contempt of court, and he can get out of jail very easily -- by complying with the order.
nor shall be compelled in any criminal case to be a witness against himself
The privilege against self-incrimination applies to any interaction which they introduce into evidence against you in a criminal case, or from which they derive information on which they then gather other evidence that is used against you in a criminal case.
It doesn't actually protect you against the police doing anything, or forcing you to provide information (other Constitutional provisions may, however), it just protects you against certain information being used against you in criminal court.
No, Miranda vs. Arizona set standards for how 5th amendment protections apply in a criminal case, and established remedies for violation of those protections in such case.