Bikes of that caliber typically are not sold on ebay, cost of shipping approaches value of bike, so no one wants to pay 2X what they can buy the bike for locally. Stop riding it, as it sounds like it has not been serviced in 35 years. So bearings and grease will be totally shot, risk damaging hubs and cones.
39 year old gum walls should be shot as well.
As far as value, depends on several factors:
1. Where do you live?
2. Overall condition (pictures)
3. Your ability to market the bike (write a good ad, take full sized pics, etc).
I cannot overstate the value of #3.
As a practical matter, the Varsity was an extremely heavy bike (40 pounds), with bottom end components, and Schwinn made millions of them. But people like them. And they are damn near indestructible.
Orange color is a plus.