I would like to see fuel dumped evenly, like the Left and Right tanks at the same time, so that the aircraft balance remains.
Absolutely, Mark. I'm with you there and I've added the item to the list.

While I understand your need for a working fuel dump procedure, I wonder why somebody would use the "manual" addition or reduction of the aircraft's fuel via the FSX menus inflight on a regular basis.
Of course, the fuel should be set before engine start and it should fit your route, some holding and those three go-arounds I always need.  :-/
Isn't that fuel planning (roughly will do!) a part of the fun when using a detailed aircraft?

The documents help you guys and, if not, the fuel flow gauges will do since you gain some experience about the actual fuel burn rate there. The 707 even records the fuel used for each engine, so you can do your normal roughly planned flight and see what was used and how close to "dry" you were.
Am I the only one wondering?  :-[