Think i have solved my surge protector problem, my panel will accept Square D Homeline breakers. They are rated for 2 wires. I didn't realize the Homeline series was capable of this. So gonna replace one of my old breakers with Square D and add surge protector to that.

I also want to put a GFCI breaker on at least one end of this circuit to pump. Wire that feeds pump is 12/2 with ground. Could i put 30A gfci breaker in main and 20A standard breaker in sub panel? And still have protection?
Is it possible to have gfci breaker at sub with only the 12/2 w/ground?