First, Dw's multi-screen does not simulate retina displays. Regarding your media-query; did you set the resolution value to match that required for a retina display?
Also do not forget that if you did set the resolution value for a apple retina display, then remember that the media-query will not match any other devices except the apple retina display at that size, unless you used the 'or' clause to also target other devices.
As for everything else you ask, forum members will have to see the site live in order to test on a apple retina device and help further, (and not everyone on the forum uses/has apple retina mobile devices, so be patient please).
Thanks for your reply! I did set the resolution value, but, instead of the 'or' clause, I used two different links for the retina vs. mobile style sheets. That worked perfectly on several (actual, not simulated) devices on a site I had done for a previous client. However, I will try it using the 'or' clause. In fact, I copied the media queries for this new site from that earlier site. Multiscreen preview did not accurately reflect the iPhone Retina option from the drop-down menu for either site.
Multiscreen for Smart Phone works most of the time, and I find that to be very helpful. However, if DW's multi-screen does not simulate the retina display, I wonder why Adobe included "iPhone Retina" in the Multiscreen drop-down menu at all. (I don't mean to criticize Adobe for it, but it does seem an odd choice to include a feature in a menu when the feature doesn't really work.)
Anyway, thanks very much for your helpful reply.