Water pump: They are all loud. You just have to get use to it. Actually, water pumps run very, very, very quiet. If you were pull the pump and turn it on, you'd barely hear it run, or hum. What you are hearing is the vibrations amplified through your camper's plumbing. There have been countless posts on this forum site for ways to quiet the system down. But the one that seemed to work the best was the guy who addatched a bunch of garden hose from the output of the pump to the trailer's system. All the pumps vibrations when through the garden hose and by the time the vibrations reached the end of the hose, there was no vibration. He said it ran very quiet. That was probably the best fix I've ever heard of.
About your hot water faucet.... the problem is not the plumbing, the problem is the faucet. You just have to turn the faucet on more. Change the faucet or remove it completely, and you'll have tons of water.
No help or suggestions on the refrigerator.
All water heaters are installed with a rocker arm on-off switch at the water heater (outside). Some RV manufacturers on some models will double switch them with a second switch inside the camper. They are on a series, which means both switches have to be on in order for the water heater to be on. The rocker arm on the water heater is a safety feature, so if the water heater is drained, it can be turned off right there, so if the switch is accidently flipped on inside the camper, the electric heating element will not turn on with an empty tank and immediately burn out and be ruinied.
No comment of your fuel station. I've never had one.