I have symptoms very similar to your. I feel like my brain is on fire many times. I have passed Mensa test in 2013, and I'm quite sure I wouldn't be able to do it again. I often feel head pressure, confusion, or I have a feeling that I'm going crazy. The things that helped my with this is Klonopin, but I stopped that because I didn't wanted to try to change something and it made my symptoms worse, but I'm still off it hoping it will get better.
I also don't have PEM that bad, more general malaise, and it more feels like the disease is affecting my brain than my body. I also was into music production before I got ill, and I really enjoyed playing and making music. Now, it's like I lost the ability to enjoy it, and if sometimes feel the love for the music again, if I start dancing or nodding my had and moving along with music I quickly loose the feeling again and become tired with lots off neurological pain trough out my body.
I noticed that cold environment helps a lot with the "brain on fire" thingy. So, I try to always keep my AC on in summer and not to spend to much time in hot environments. At least it helps my symptoms in the short term, until hopefully I find the real solution. And I actually think that being in cold actually decreases some kind of brain inflammation that I have and even slows down the deterioration in the long run.
I'm wondering do you also find that heat increases your symptoms since, your symptoms sound a lot like mine?