Parts drawings here:
And I suspect you actually have a 99Minnie wf331C, rather than Minnie Winnie! There are actually both but only one has a 331C model, so check that for "proper" name to get to the right place?
Plumbing drawings are a bit on the older side but some info there.
I did a couple snips of valves under the bed--if my guess is correct on right model?
I would say those under the bed are just tank or low point drains.
I did notice a bypass valve on the water heater backside that you may want ?
My first guess on the pump is that there is a valve open, either letting water from the tank move to the pump and then back to the tank OR that there is a valve letting air into the pump, so that it can't draw the vaccuum needed to move water as it is easier to move air as lighter than water.
One good place for this to happen is if you have a valve for sending water to the tank or inside for direct use. If the tank is filled and this valve left in the "fill" position instead of moved back to "normal", the pump sucks air.
A second common problem is the little filter at the end of the pump is a very thin little plastic bulb and freezes quick and easy, so it may need a check. It can give a crack right at the input to the pump and suck air there.
A different problem with the low pressure and not shutting off is a leak in the line from the pump to faucets but those are expected to show up as leaks and water in the wrong places, so I tend to think it is sucking air before the pump rather than a problem after.