My situation is similar to yours, 65 and ride a flat bar hybrid (till last year when I added road bike) and had similar issues with upper back and shoulder pain.

A couple things helped:
- More than anything I got some PT and started more focused upper back exercises, the cost was nothing compared to the benefits

- Don't "work through it" by riding longer when the pain says stop, build up slowly

- Move the saddle up to shorten the length of your reach

- Barends help some, check the Ergon grips with palm support. Your Crosstrail may already have them

- stop and stretch rotate your shoulders and stay loose


Good luck