The AD has the specifics
>What do you guys do if you have less than 2500 in the center as ramp fuel, do you just leave center pumps of and start them after 10000?
Per the 757/767 AD, that's exactly correct.
>Press-light illuminated and flickered
One of the specifics written is that "A center tank fuel pump must be positioned OFF at the first indication of fuel pump low pressure at any time during flight. This includes low pressure indications that may occur as a result of pitch attitude changes."
For the 757/767, "approximately 500kg of fuel is required in the center tank to ensure the fuel pump inlets remain completely immersed when the pump switch is ON"
That is the intent.