Black Holes have 3 properties, which are observable (and hence measurable): angular momentum, mass and charge. Volume or radius are not properties of a Black Hole and are unobservable. Hence Density, doesn't make sense so neither does anything you say here about density.
Yes, you could shrink a pea to something like a primordial black hole. It will still only weigh 1 gram and have a tiny event horizon and still only have the gravitational field of a 1g pea. It would attract mass that was very close and would grow, ejecting energy from friction with items crossing its event horizon - in theory it could swallow the Earth, but no way the Moon as the Moon would just continue orbiting it after the Earth was swallowed - except if ejecta from the Earth created a cloud of dust that slowed the Moon enough to fall in...
The Universe may be full of such Black Holes and they may even be constantly passing through the Earth causing subatomic holes from one side to the other that seal over and we never notice them. They are candidates for Dark Matter - a kind of "strongly" interacting massive particle .
And again density makes no sense. We talk about the density of Neutron Stars because they do have a radius and a volume.
