The hydrogen orbital, for example, is approximately spherical/toroidal, which matches the radial distribution plot of QM.
Ionized hydrogen has a delocalized electron; it is not gone — but rather elsewhere. In our model it is enmeshed with the others in the column.
Speed is used as a surrogate for momentum because QM doesn't allow us to deconstruct the speed/direction from the momentum separately. Ideally we could illustrate a more cohesive motion as well as faster for greater momentum.
Current is transfer of motion from the high-momentum, high-V, shells to weaker ones.
I have briefly discussed resistors and other elements of circuit in other threads here. Check it out and let's talk there.
Concerning your comment about vacuums, we have to understand that there truly is no vacuum. We assume that when atoms are isolated, their surface pressure is decreased such that they can occupy tremendous volumes. Currents in outer space are present with 8.49×10^-23 atoms per 10 cubic centimeters.
Hopefully we can move toward capturing QM, and ED descriptions of electricity. A magnetism video will follow soon.