Sounds like your life health priorities would dictate more bike time.
The more you ride, the more you will benefit from riding a new or newer than 50yo bike.
and Super Congrats
on health improvements. You stated, weight loss without exercise, but were riding your bike?!? Riding is exercise. A newer bike might help you exercise harder without pain - as in lower gears for hills and probably a better fit to your body and riding style.
edit: Yes, there is better gearing for hills with newer bikes. And your components (while functional) are lower end stuff even for their times. The best thing is to visit a bike shop that sells new and used bikes and make your own determinations. I ride old bikes and gearing modifications are not always simple. Want to learn to wrench vintage bikes?
Here are my Austrians - each about ~40 years young. They have components appropriate for their vintage, even tho acquired as frame & fork. The Michelle still had some original components when I got it.
AustroDaimler Olympian
AustroDaimler Vent Noir
AustroDaimler Michelle