1. yes
2. no. you won't find a quick disconnect that will fit on a concentrator.
3. yes
4. teflon tape on any NPT (national pipe thread) connections. If you are using normal hose "B" style connectors, don't use any tape, seal is metal to metal.
5. Not really needed for surface mix torches, but if it makes you feel safer, by all means go ahead.
Done good, kiddo!