Nick,

I would hold off on the MRI if it is just to measure for CTE (shrinking). It will takes years of shrinking before an MRI will show the difference.

Slow down. Get your teeth out and your jaw healthy for a while, then start looking for new ideas.

There are medical reports of people who became psychotic from abscessed teeth, especially the top teeth. Once the abscess was healed, they recovered. I wonder if you decline last fall was not because of the marathon of gaming but instead from your tooth getting to a critical condition. Jaw clenching during an intense game could have caused a problem.