Circuit 450 (blk/wht wire) is just a ground wire. It will never have current.
I imagine the Pink wire goes from the sending unit to the fuel gauge, as no other wires come out of the sending unit and the fuel gauge has to get it's info from the sending unit somehow.
Under normal conditions with the key off there should not be any current/volts on the red fuel pump jumper wire. If there is, this usually indicates the oil sending unit is bad. (I don't know about when the key is on)
Put your live 12v jumper wire back onto the red test wire and leave it there when checking for current on the Grey wire. You can check for current with a test light or volt meter, but in any case make sure you get a good ground when testing with your meter or test light. (Since you say the pink wire has current, you can use this same source for a ground when testing the Grey wire and you will know you have a good ground)
If you have NO current on the Grey wire, then the relay or PCM is probably bad.
If you have current on the Grey wire then use the black wire for a ground from your meter or test light. If you have a light/volts between the blk and Grey wire the fuel pump is bad.
If you only have current on the Grey wire when using a ground other than the black wire, then the black wire (Circuit 450) is not making a good ground.
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By the way, the cover on the relay box in the glove compartment unhooks from the bottom. Don't know if you ever got that cover off or not. There is a tab on each side that you press up on and the bottom of the cover will come loose. You have to have everything out of the glove compartment to get the cover off. There are two relays in there, both are the same kind/type, the one on the left is for the transmission and the one on the right is for the fuel pump. You can swap them to see if it makes any difference on the test wires.
Good Luck,
DelC