Prima facie letter does not give you right for work authorization. However, you may be eligible for some benefits, depending on state laws. Look at HHS.gov website for HHS-funded benefits explanation. You can also apply at your state welfare agency and see what happens.
A prima facie notice allows I-360 VAWA self-petitioners to obtain certain public benefits as "qualified aliens." Depending on where the self-petitioner lives, that notice may permit him or her to obtain a driver's license. It should also allow self-petitioners to obtain some public benefits (not SSI or food stamps); the notice lets the public benefits administrator know that the self-petitioner qualifies.
Unfortunately, only approved VAWA self petitioners are eligible for an employment authorization card.
You should check in with an immigration attorney familiar with VAWA to help you with the case. USCIS may still ask for further evidence, the prima facie notice does not mean the petition is approved, rather it just means that the petition has been filed. Also, you may need to ask USCIS to issue you another notice if there has not been a decision in 180 days.