Katie,
I agree with the last couple of posters. It doesn't matter what you do or don't do, if your son wants recovery, he'll get it. If he wants to use, he'll use. So put yourself first, and if that means telling the pastor (you don't deserve guilt over this!) then go ahead. Addiction wants us to keep secrets. Shine the light on your son. Anyone else he stole 1000 dollars from would certainly do so! Once you tell him that, since you're going No Contact, then the ball is totally in the pastor's court, including any funds he raises through the church.
What a complicated and painful situation. I'm so sorry but keep pushing through! Hugs and love from NC.
<3
-Holly