Most important things in life are family, friends, and health. If you have those 3 things consider yourself blessed. I always try and put those 3 things above work, even though I work a lot, because having those 3 things is so vitally important.
Even with the three other things you mentioned, not feeling like a contributor to society must be really hard.
Might have to get a niece or nephew to crawl behind a desk to plug in the odd dongle, I suppose. Whippersnappers.
I would find those videos fascinating. You might be able to set up an AMA-style thing where people ask questions about what he did, how he did it, why things were done in that way.
Do you have anything similar to U3A where he is? It's a nice way to meet other people and keep your brain ticking. https://en.wikipedia.org/wiki/University_of_the_Third_Age
I will look into U3A and similar options locally, thanks for the idea!
There was a man at the church I grew up in who was seriously disabled in an industrial accident who volunteered 40 hours a week at the local library. Similarly my grandmother volunteered at a hospital into her 90s. In her case it actually saved her life when she had an aortic aneurysm that almost certainly would have killed her if she hadn't already been at the hospital when it happened!
2) Helping others is another thing that is incredibly rewarding, mentally at least.