I'm confused too. The town manager wants a letter from you confirming your verbal request to retire in five months at the end of June. This would be because he/she can't start the retirement paperwork rolling without a written request from you. That's standard policy for most any employer. Employers just don't start a retirement process based on a verbal request, ever, for obvious reasons.
Now you want a letter from the town manager saying your job is safe? Are you worried they are going to boot you earlier? Why?
If your emotions are flying high due to the riff between yourself and your immediate boss, this would be a good to take a deep breath, calm down and prepare to go through the motions of doing your job for a few months and then retire. Try not to make it into a soap opera.