Hi Ben, I am sorry to hear how you are feeling this week. My symptoms are quite similar to yours (headaches, brain fog, fatigue, some memory impairment and concentration difficulties).

I am sorry but I am unable to give an educated answer to your question, as Mark will surely do. Have you thought about giving yourself some quiet rest to see if that helps? I would certainly not quit all activities for an extended period of time, but a few days of rest to go through the relapse would perhaps be useful. I sometimes do it (for 24-48 hours) when my symptoms are too strong.

Have you invested in good shoes? I personally find hiking shoes to be the best, but there are also some comfortable sneakers or running shoes, as I already told you. Walking shouldn't be a problem with these.

To reduce the inflammation, have you started an anti-inflammatory diet? I think I mentioned that to you already. Many people on these boards have had good results with it, in particular for the sensitivity that many suffer from. It takes some discipline and patience, but it is probably worth trying. You can see these threads for instance:
Update on diet and PCS
An unusual head injury

There are many people on these boards who recovered well even after a prolonged period of post-concussion syndrome; perhaps you could try thinking more about these cases than about the nightmare scenarios that seem to obsess you?