Do you have a multi meter? Is the battery dead? Seems like a silly question, sorry. If that's all your going to run off your fuse block, you might not need that heavy duty thing. The only thing drawing the most amps is your bilge pump. I'm guessing around 15 amps. You won't need the ground bus bar if everything is on the battery. The negative side will essentially keep everything grounded.
I would think you only need something like this.
You just need to hook up the positive side of the battery to the post. Then properly fuse each output. Then run a return line to the negative terminal of the battery.
Most of my experience is navy radios and wiring police cars with all their sirens,lights, radios and what not.
Our grounds were essentially the body of the car which is connected to the negative end of the battery. Just pay attention to your wire Guage too.