I've had similar problems, and can endorse that the ergonomic modifications really do make a difference. You shouldn't need an attorney; the Office of Civil Rights is quicker and even more effective than OSHA, as ADA (Americans with Disabilities Act) mandates modifcations like that, and you certainly appear to have plenty of documentation. If your company has any familiarity with ADA, it should get them moving; those folks can get pushy...

Meanwhile, for yourself, try a bean-bag lap desk (SheWorks sells one; there are others) for your keyboard--it's a really quick and cheap solution ($35?)