Are there formal guidelines for the development of software that help minimise health risk from software, covering issues (mainly related to GUI design) such as:
This sort of stuff in general?
A good starting point is the ADA website.
See also IBM's accessibility site.
See Section 508 for information on accessible software. This does cover things like maximum blinking/refresh rates that could cause issues with epilepsy. For an example of a form venders can use to judge there 508 compliance and by association general accessibility see http://www.itic.org/index.php?src=gendocs&ref=vpat&category=resources While following section 508 guidelines does not guarantee software will be accessible to all users since it does not cover what technologies each assistive technology product such as Jaws or NVDA supports it’s a good start