fouled fuel problem

I've got a serious fuel problem. I haven't ridden my 1990 K75 since last fall. I tried to start it today and couldn't. It didn't seem to be getting fuel so I checked the gas tank. Yikes! reddish sediment fouling the entire fuel gauge sender unit, deteorating gasket at the base of the fuel pump; fouled and detereorating fuel pump filter gauze breather hose, reddish sediment caking the fuel pump electrical terminal nuts and the gasket nuts that hold the fuel pump gasket it place. There's also some reddish streaks throughout the fuel tank itself. I've removed the gas tank, taken the fuel filter out (which astonishingly seems to be fine but I'll replace it anyway), removed the fuel pump assembly from the tank, and removed the fuel gauge sender unit from the tank.
Now what; any suggestions on what caused this disaster? I'm guessing it has something to do with the ethanol in our gas here in Oregon and also the additives I put in the tank to deal with the ethanol and water.
I know I have to clean the gas tank; any suggestions on what to use. And I'm guessing that I need a complete new fuel pump assembly, new fuel gauge sender unit and new fuel filter. Is there anything else I should be looking for?
Also, any suggestions on what to use to treat ethanol laden fuel with to prevent a reoccurance of this problem?

Redish...could be the inside paint of the tank slowly chipping away. I clean the filters inside my tank ('88 GS) every 2 years from what looks more like red chips.

/Guenther