Can I sue someone in civil court for making a death threat against me

You may have a cause of action for things like intentional infliction of emotional distress. Speak with an attorney in your area. Did the death threats cause you a lot of problems.

In short, yes -- depending. If you had a reasonable apprehension of an imminent battery and he had the apparent present ability and opportunity to inflict that battery, then you satisfy the elements of a civil suit for assault in Pennsylvania. The bigger question may be, if you get a civil judgment against him, will you ever be able to collect on it? You can't get blood from a stone -- is this guy a stone? If he's in jail, he is. Feel free to contact me if you'd like to discuss this further.