change the batteries I do not actually think this will solve the problem; but, the 3000 has given us truble and the batteries have often been the culprit.
when we have had trouble in the past it was the furnace not shutting of.
without being there I would say jump out the tsat see if the furnace will run long enough to raise temp to 72.
the 3000 does not have an adjustable swing. There are no backdoor adjustments. So if the furnace runs properly when jumped and batteries are good change the stat I would recommend a Honeywell 5000 or 8000 iaq if you need setback but a Robert Shaw non-programmable or a Honeywell T87fa would be my choice.