I just need to figure out how to make an internal combustion engine pull from zero rpm?
They do. Just not that much.
A compressed air engine is a pressure engine. The energy is stored as gas pressure (static pressure) it will produce a force on the piston as long as the inlet is open. Once the inlet is closed the pressure will drop as the gas expands (pinching energy from the surrounding to do so).
A steam engine has the static pressure from the boiler, but it also has a lot of energy stored as heat that allows the gas (water vapour) to continue expanding without the pressure dropping much (it has enough energy to be expanded two or three times while still doing useful work)
An internal combustion engine has some of pressure form the chemical conversion of liquid fuel in to gas, but most of the energy comes from the heat of combustion. If you can keep the heat in the cylinder, the gas will continue to push on the piston.
Of course the dilemma is that while a steam engine will never get hotter than the steam, an IC engine will get to a very high temperature if not cooled in some way.
So, how about a total loss internal water spray cooling system?
Bill