would it be possible to turn your welding apron around back wards? that is a pretty sensitive area to catch on fire by catching sparks in them pockets and not notice for the length of a welding rod while welding.
try a local welding supply store or a welding shop for suggestions what size and length cables you need and they can tell you size connectors for the size cables you get
fill with soapy water till it is totally full and water is running over fill valve leave set 2 days then strike match near valve you may get a light puff out fill valve. be sure tank was level so no voids in tank to trap gasses. then start cutting or drain then cut. just the way i do it and...
no it is not safe to breathe though we did for about 30 years then OSHA moved in but they still didn't catch em all but only when we had to cut or weld it drilling or punching holes not as bad