A picture or two would be helpful so we can better advise you. You have some kind of through hull fitting, then a gate valve, then the pump, Right? If that's what you got, then the purpose of the valve safety. If a case fails, you close it, so your boat doesn't sink. I wouldn't remove it.
Not sure about the white wafer thing, most likely a fuse to protect your pump. If so, you should replace it with a fuse of the amperage that the pump manufacturer recommends. There's a lot of guess work here. That's why pics would help.