I had this same issue when i bought my '98. Your tripmaster battery is going bad. It is located deep within the tripmaster unit, and needs to be replaced. It's coated in several layers of hot glue and spot-welded to the terminals. Open her up to find the proper battery # and purchase a replacement. They're $5US.
As for the circumference adjustment, you must hit the down arrow many times. It will cycle through several times with erratic numbers and eventually display a declining sequence in numerical order. But you have to press the down arrow nearly 100 times. PM me if you have other questions. I may be able to find photos. Very easy fix.