My 1970s vintage Lyman manual shows 6.5gr Unique under the 230gr FMJ as their "factory duplication load". It also lists 5.9gr for the 185gr jacketed bullet, but that is for the swc target load.
I know its "old data" but I'm an old guy (now) and I've been using it since it was "current / new" data, and see no reason to change.
Min load would be whatever is just above sticking the bullet in the barrel, although most prefer something that will actually cycle their pistols, and that will take a bit more.
Max load? as others have said, just before your gun comes apart. Of course, finding that will cost you the gun, but there's no free lunch, right?
Max safe working load will depend on what gun you have, and how it is set up.
I've got a hot load for the Speer 200gr JHP (with Unique) that works fine in my SIg, but craters primers in 1911s.
Unique is not as clean burning as some powders, but in the .45ACP I've never found it to be the "flammable dirt" that I have seen some others claim it to be.
All in all, Unique is one of my favorite powders, had always given me everything I asked of it, and has been doing it for me for well over 40 years.