GOOGLE what a PVC ball valve is. Im currently setting up my own livewell and Im using a 12V motorcycle battery (since I have some laying around) running a simple tsunami 500 gph (Gallon Per Hour) and plan on using the same power source for my FF. A 500 GPH pump is like that water fountain at school that always squirts you in the face and out of that fountain but not much more than that. Your outlet 3/4 the way up is fine. if you mount a PVC ball valve (google) or the friendly plumbing dept. at Lowes can show you.... mounted inline between your pump and bucket sounds like a $0.60 solution.
Good Luck!!!!
Jay