Pics. would help and you have more than 2 questions(J/K). I will answer some and somebody else will chime in. The big gasket will go from the regulator to the co2 tank i don't remember about the small one. The plug will go to your PH monitor/controller which will tell your seloinod when to open and close . Mine c02 tubing go on top of the bubble counter.It will help if you have the PH monitor/controller, so you can read the effleunt PH and fast reading the display too.
Reefing is just like cooking, all the ingredients have to be just right , except you don't have to bring the water to a BOIL...