I wish for the healing to be fast. That doesn't look so pleasant to have to deal with.
I couldn't image using an eBay or clearly china made fitting or hose, especially a brass fitting with HPA. I don't like can filters either, too spooky for me. I have an AV 4500 compressor and have filled two large Scott tanks quite frequently over the last five years. I use good stainless steel fittings and remove all the extra connections I can when filling the tanks. I also secure the hose just in case.
I have had a few burst disks pop over the years while filling. The first time was exciting, but after that no big deal. I do use a check valve, but it is built into the Stikman fill assembly that I use, so no extra connections with an in-line check valve to worry with failing. I always fill to 4500 psi, but I don't stand around while doing so. I set a stop watch and leave the room, coming back every 7 to 10 minutes to bleed off water and check temperature. I also use the auto shut off, but don't fully trust it, even though it has always worked.
I do have a safe I am not using sitting right next to where I fill, but never thought about using it while filling. Not a bad idea, but I will still be exposed to the hose, fittings and tank while filling my guns and traveling with the tanks. So, I don't know about the safe thing and using it. I don't worry too much about the tanks exploding, except while traveling in the summer heat or in an accident. I take precautions there, too.
Be safe out there and plan ahead...