Re: The FRB is well outside the Milky Way, at 5.5 billion light-years' distance.
A radio telescope cannot measure the distance to a source. It can only measure the DM (the burst is detected later at lower frequencies). The standard interpretation is that the radio signal traversed a tenuous plasma in our 'own' Galaxy and - if the RM is larger - in the extragalactic medium or near the source.
The large circular polarization of 21±7% for FRB 140514 hints at extraordinary conditions at the source. A distance of 5.5 billion light-years for FRB 140514 is an upper limit.