Unfortunately, re the name of the ship that massacred the crew, as far as I am aware, no. I personally spent a great deal of time some years ago liaising with a very knowledgeable person / author (with regards the IJN) - who also had an abiding interest in the question - trying to sort that mystery out and we never could reach a definitive conclusion. Several times we thought we were very close, only to run up against a brick wall. All we eventually came up with was that it may not have been a DD at all.
As for Augustina witnessing Pope's sinking, again no. Only a inference, from what is written in the book Japans Blitzkrieg by Bernard Edwards - and given we now know from where her wreck lays that she was in the vicinity - that she may have seen the planes that attacked Pope and heard the bombing. Attached is an excerpt from said book. And that inference, IIRC, given the timing of the attack, was that Pope was the only ship being attacked from the air in the vicinity of where we now know Augustina was at the time (which was certainly not off Bali as the author asserts.)
If one just goes on the bearings, that is where he states that Moerman (Augustina's captain) said the planes came from (north) and where the explosions were heard ("in the direction of Lombok Strait" - which would have been south east if she was north of Bali) then it 'fits' for what could have been an attack on Pope (given that we also know approximately where Pope was circa that time).
Save for the silly reference to seeing the 'tall peak on the island of Bali to starboard' - which Moerman surely didn't say - and a few other oddities (he names the Jap ship as the DD Harukaze) it seems much of what he has written though may have came from Moerman / or a report that Moerman made re the sinking and aftermath, and is the most (only?) detailed account I have seen of Augustina's sinking, and runs for seven pages in the book.