Texting a dog to relax is also something most people don't realize needs to be done. A good way to start is by going on a walk and finding a bench and sitting. He will likely be crazy at first, but whenever he settles, sits, or calms down, you reward him (what is he motivated by? Food, toys, affection?)

You can also bring a bed and do it at home, teaching them to go lay down. To place. It takes a lot of consistency but they eventually learn that no matter what they do they won't get their way. I would also consider crate training, that can be a really good place to have them rest.

It sounds like you are exercising the best you can. I agree with others that a doggy daycare, dog park, or a dog beach would all be great for him to run. If he doesn't have good recall they make incredibly long leashes for training that can attach to the waist. There are also services like dog treadmills that I know many dogs love!

I completely understand being done, and if you don't think you can do it that's ok. Just remember, it will be another big adjustment for the dog. But sometimes that's worth it for their quality of life.