I think just transfer him from LFS to home and into QT without feeding, ammonia is not the problem., does not matter what the test said. I have never test for ammonia in nearly 30 years of reefing. I think your Melanurus died form stress/stress induced injury. I have lost wrasses, but never other fish, due to transfer induced stress.
My QT protocol is to put them in a QT reef, 40 gal with sump, with sand bed, fully lighted and with coral and clams in it. I also use this tank as a frag tank when not use as QT. This tank can be diverted to isolation with it's own sump or diverted and move the return pump to the main sump to put it in the same circulation with the main system. I don't treat new fish for disease unless I see it while in QT. IMHO, TTM for me kill more fish than the number of fish save by doing this method trying to control Ich.
Regardless of what you do for QT, it is reasonable to get the fish settle and stress free before initiate your protocol.
Stress induced injury could be a possibility also, he was thrashing around in the bag a good bit.