Let me preface this by saying that I've hardly touched Safe.pm. In fact, my reply to one of the links you noted was the first and only time I used it. I hope that what I present below is not out of context. As usual, please correct me where necessary.
From what browsing I've done, Safe.pm doesn't seem to have been improved upon anytime lately. Although my post doesn't answer you questions about being safe or not, it does point out that it may have other problems. I came across this thread between Tim Bunce and Jarkko Hietaniemi from 7-2001:
TB: Many people who use, or try to use, Safe could get by with the ops pragma
(which is why I separated the ops filter logic from Safe many moons ago).
JH: Is this still true in the days of SOAP, XML-RPC and... insert buzzword here?
TB: Perhaps less so, but Safe is still (from memory) fairly broken/limited
in assorted dimensions many of which can't be fixed before perl6 and the others probably need a rewrite (probably to use ithreads).
This view seems to be mirrored by a few other non-PM search results, but were not from as well-known figures. Unfortunately, they leave us to our own imaginations as to what these dimensions