To release connectors from the blue ground bus terminal you can use a screwdriver. You just need to put the screwdriver in the corresponding hole and turn it firmly counter clockwise. I’m not sure whether it’s supposed to be phillps or flat; I’ve used both with equal success. I’m not sure how to remove the bus from the rail; I’ve never tried that.
I’ve read that you can use regular blade style fuses in that fuse bar, but I’ve never tried that myself.