the matter that is inside a black hole has little or no energy.
the electrons of atoms that make up the matter inside a black hole have moved as close to the atoms center as they can move , their orbits have decreased so their energy has decreased , their orbital velocity has decreased , if not stopped.
this energy is contained by the mass until the mass is able to shrink further by releasing a gamma burst.
the more a black hole feeds , the more energy it will release.
then T goes to infinity as D is streatch to infinity
D could not stretch beyond the distance from b outside the event horizon to the center of the black hole.
D would still remain intact or constant as a measurement.
I don't think that gravity travels at all , and I don't think that gravity has waves , it is a constant (proportionate) to the amount of mass an object has.