Sounds like a bad master.
How are the rears locking with the pedal at the floor?
The master is setup with 2 different reservoirs, one for front, one for back.....so if you don't have a massive front leak somewhere, its time for a new master.
Also, it is possible to bleed the new master like a standard style master....but to get a perfect bleed, it WILL need to be connected to a full diagnostic system to put the ABS in bleed mode. Most shops do not understand this.....