If someone records you without your consent, they can be liable to you for civil damages (of $100/day or $1000, whichever is greater), under the Pennsylvania Wiretapping and Electronic Surveillance Act.
If you are interested in pursuing a claim, you should contact an attorney.
Leo M. Mulvihill, Jr.
The Fishtown Lawyer
2424 E York St, Suite 316
Phila, Pa. 19125
In Pennsylvania, both parties must consent to recording.
The listener can testify as to the threats without the aid of the recording.
Your boyfriend should confer with counsel, in person, and not over the open internet--that is what got him in trouble to begin with.