bag of carbon on your skimmer, are you running ozone?
It's just to take away any smells that lie about in the cabinet.
I don't think you would grow much with that, freshwater i guess.
Dont waste money on replacing those foam blocks. Rinse them in old tank water and keep reusing
Yes should pair up on its own.
I dont spot feed mine anything in perticular. It eats what it finds, usually pellets that the fish have missed etc