Phil Burt's Bike Fit¹ is great read on the subject, with lots of in-depth advice and solutions. I suspect the vast majority of the readers are Sunday Morning Warriors, but it does cover more relaxed styles which are likely more applicable to you given your bike. From the book:

“Some cycling ailments are confined to the elite and some to recreational riders. It is unheard of for me to see [...] our national squads with numb or tingling hands. However, I have seen serious recreational cyclists with quite debilitating hand-nerve injuries referred to me by local doctors.”

A good chunk of the book deals with off-bike stretches and flexing to cut down on injuries too. I've found better off-bike care has helped me a lot, and I know a good number of cyclists who swear by their yoga sessions.

Hope your situation improves!

Edit to add: He also has a few videos on Youtube with advice on improving your fit for comfort and pain relief, which is a cheaper option than the book ;)

¹ https://www.amazon.co.uk/Bike-Fit-Optimise-Performance-Avoid...

I've gotten relief from hand problems from typing, cycling and other strange uses by doing push-ups.

My sports med doc told me this: if activity X is causing you pain you should cut the amount of activity X you do by 50% and if the pain doesn't get better cut it by 50% again, take some rest, if you have to.

On the way back increase your workload by 10% a week if you can do so staying pain free.

It seems agonizingly slow but it means I go from short easy hikes at the end of the Winter to getting 20,000 steps in before 8am in August.

A seat like Selle Royale Respiro or Ellipse (available in multiple widths, I get the widest I can) with "elastomers" underneath were the biggest boon for me cycling on a regular bike (I am 6'5"/195cm and ~100kg). They are roughly in the $50 range.