Keep the Rena away from the rocks :slfg:
I would use Seachem Prime as a water ager after the one you've been given runs out.
Don't use the pH up or down, The pH will find it's own balance naturally.
I wouldn't use the algae clear or Aqua clear, It's better to find the source of the problem and fix that, than it is to just treat it.
Don't know anything about the filter, but if you cant find parts the Aqua one CF1000 or Aqua one CF1200 will do the job nicely and parts will be readily available.
The clear plastic things in the air lines are check valves that stop water flowing back down through them if the air pump is turned off