[Clodfobble]

If I were the person looking at your cover letter/resume, my one big fear would be that you were still incapacitated in some way by your CO exposure. Obviously you have to explain the time gap, but I would spend the first part of the cover letter highlighting your experiences as a librarian, etc.--and only after you've established that you're an excellent writer, not just in work history but in the cover letter itself, about halfway down the page bring up the reason for the employment gap (making sure to make it sound like another qualification instead of an excuse.) Incidentally, I'd also focus more on the homelessness than the actual neurological damage aspect of it.

If the cover letter starts out with explaining the employment gap, they may never even get to the resume part. Anyway, I think you could definitely do this job, and I agree with slang, trying to talk to someone in person would be the best way to go about it. Enthusiasm is much better seen than read. Good luck!