Shkelzen,
Did you ever resolve this? If not, this error about the UME persistence configuration looks suspiciously like the error I was getting when I tried to create users in the ABAP store via the Java UME, and/or when the Create Users step in the Managed System Configuration for the Java stack of a dual-stack system would try to do the same. The cause turned out to be that the SAPJSF user did not have write authorization in the ABAP system, i.e. only had SAP_BC_JSF_COMMUNICATION_RO (Read Only) assigned. Assigning the ABAP role SAP_BC_JSF_COMMUNICATION to this user and restarting the Java stack resolved the problem for me.
Regards,
Matt