I hope so

The first time I got CFS I was 19. It lasted 2-3 years before I went into remission for about 10 years. Maybe the same thing can happen to you!!
Its really impressive that you can do some running again
I also think it's a significant improvement, in the past, every time I do some exercise, I felt like I ran out of the energy and I would be extremely tired, at that time I think exercise may have the opposed effect.
But the brain fog is an inevitable obstacle in all the daily activities, maybe I need much more time to see the improvement of this aspect.
Recently I read a book, there's an idea willpower is directly related to the energy you have and another book give many examples about the relationship between exercise and intelligence.(Spark: the revolutionary new science of exercise and the brain) And an example attracting my attention is that one grandmother keep active and a sharp brain, however, after an accident, she gradually lose her action ability and she becomes more and more clumsy.
I think the reason why brain fog is hard to relieve may is that it's hard to make CFS patients be able to reach the point having enough energy to do exercise.
I have tried so many things to improve the cognition, all I can feel obvious side effects, now I only use a few things to maintain energy and strengthen immune system.
After 7 years, I find everything comes back to the simplest treatment and idea.