DruceDeVille,
As far as "character statements" I do not see the value of submitting them. Your character is not an issue, and as far as your conditions, I would only submit something if you do not have it documented by your physicians. However, the inevitable question is why you don't have documentation. This is another reason why the Independent Medical Advisor can help.
As far as commander's letters, here are some links:
Commanders Letter? Formal PEB - I Need advice
For various reasons, probably most importantly because each case is different, I do not post templates.