1. The penny doesn't really have a "shell" - even if it did, it would be composed of atoms, just like the rest of the penny. The shape and structure of the macroscopic structure doesn't really influence how the electrons behave in this case.
2. The electrons do not attract each other; they are all negatively charged, and like charges repel.
3. Electrons do not "jam" because they repel one another; jamming would require that they come into physical contact, which does not happen at these energies.
4. It's true that the electrons don't have enough speed to escape the penny - however this is not a complete description of what is taking place. The electrons are being influenced by another, stronger force.
5. The electrons are attracted to the billions of positive charges in the protons. The electrons would need a significant amount of energy in order to overcome and escape this force.