I was hoping that Lou might answer this for you. After all, he flew these beautiful planes in real life.

Fuses / Circuit Breakers
Just eye candy. I thought at one stage they did do something, because of a problem with my navigation lights, but they work fine now regardless of where I place those fuses. I try to make sure they are "IN" before a flight, but sometimes I forget. My flight goes the same way anyway. No known effect on my part. Not now anyway.

Fuel Dump
When I did it, it dumped the whole lot! Not a drop of fuel was left. That was back in v1.1 or 1.2 (I think). I have dumped fuel in v1.3, but because of my previous fuel dumping experience, I monitor it very closely and have never let it get to that point again. The fuel is dumped from the outer tanks to the center tank. Left Tip, Right Tip, Left Aux, Right Aux, Left Wing Tank, Right Wing Tank, Center Tank. It might be right then left, but this gives you the idea of dumping the fuel. When you get to the larger tanks, because they drain one side first, this creates a large weight discrepancy between the left and right side, make sure the autopilot is on first!

Fuel distribution / valves
As long as the Fuel Valves are open (horizontal) (vertical), all engines will receive fuel from any tank that has its Fuel Boost Pumps on, while all the other Fuel Boost Pumps are off.
I.e. If I turn the Fuel Boost Pumps on for the Center Tank, while the rest of the Fuel Boost Pumps for the other tanks are OFF, then the Center Tank will provide fuel to all engines. I usually have the Center Tank feeding all the engines after takeoff, when everything is performing as it should. Sometimes I wait until I'm at cruising altitude.
The Reserve Tanks fuel flows into the #1 and #4 tanks if the Fuel Valves are open and as fuel is drained from them. If fuel has already been drained from the #1 and #4 tanks, fuel from the Reserve Tanks will immediately start flowing into them when you open their Fuel Valves.

Hope this helps.

Mark

Edit: Fixed error in Fuel Valve position when open. As pointed out by buedi here: http://www.captainsim.org/yabb2/YaBB.pl?num=1310307246/4#4
Sorry.