Reading through your descriptions it sounds like some are modelled correctly, and some aren't. i.e.

If you "switch off ALL the cross-feeds valves AND the boost pumps",  the engines are designed to continue to run just like in a real C-130 through gravity feed.  Only if you climb quickly with the boost pumps off would you expect to see come possible engine fluctuation that could lead to a compressor stall.  If I remember right the only way to stop fuel to the engines if pull the fire handle, or place the condition lever feather.  I believe in both cases it's closes the fuel value.

On the hydralics, some of the items such as the brakes would have one brake application with the pumps were turned off.  The others shouldn't operate excect for the flight controls.  There is another switch for those, and even if you turned that off you would still be able to fly the plane because the C130 flight control are cable driven.  It takes a lot more muscle, but in a flight sim you would feel it anyways.

The suction boost pumps assist the hydraulic system, but you would only see a temporary large drop in pressure, while operating the landing gear or flaps.  Otherwise it should have an effect.

Doesn't sound like the electricals right, though there are a lot of electrically switch you have to turn off.  Each generator, inverters, and even then you have some things hot wired to the battery.  i.e. one of the radios, of course if you turn that off. It should be off.

Anyway, there are a lot of redundant systems on the Herc.  It's a fantactic plane to fly.  Engineers feel free to chime in, I really stretching my memory here.  :)