In looking at HVAC vacuum pumps such as a Yellow Jacket or a JB, is a gas ballast needed if a dry ice trap will be used to protect the pump?  Is it a good idea if alkanoic acids such as acetic acid might be distilled some day?

This kind of pumps are not suited for aggresive gases or vapours. Even with gas ballast the pump will corrode, even if the oil is changed often. Use an aspirator, the vacuum is sufficient for distillations if water is cold and you have no problems.