don't get drag into it

You are doing your bf a big favour by telling DA that you don't want
to press charge. I don't think you should do more than that. It
is his problem and he needs to deal with it himself. You don't need
to be a white knight to save him. For him to pressure you to
lie for him at this point is outrageous. It is strange that the DA
didn't place a restrain order on him to stay away from you. In fact
you shouldn't talk to him until he gets this problem resolved.