By volume I meant that BHs can grow in surface area.

The most challenging BS is imagining that the singularity sends energy some where. I have no idea if this evaporation from the center of a BH exits. If it did It would amount to a loss of mass in BHs that aren't eating. I know of no such data
I gravitate to dark matter coming from the annihilation event only because there is no other event that involves such gargantuan amounts of matter and energy except for the earliest events of the big bang.

If everyone offered some explanations of these two mysteries we would probably still be wrong.