This comes under the rubric of "the best defense is often a good offense". Go to the court when the Prosecutor asks you to be there in his criminal case. Be prepared to explain what happened. The judge will see that your sister's BF is doing this BECAUSE you filed charges. If you can get the prosecutor to share the information or charges in writing you can show that to the DVPO judge.
In Tacoma, "former cohabitants or roommates" is broadly interpreted. Domestic violence orders tend to get handed out like candy, but the court has the ability to re-align the parties if the court understands that the abuser is going after the victim again in this arena.
The YWCA has counsel available who can help you. I hope you call him; his name is Kevin Rundle and he can help you. Elizabeth Powell