Final answer:
The most important measure of progress to track is the actual work.
Step-by-step explanation:
The measure of progress that is most important to track in this situation is Actual work. This is because tracking the actual work done allows us to compare it with the allocated budget and the overestimated total project cost. By monitoring the progress of the actual work, we can identify if the project is on track, behind schedule, or exceeding the budget.