I purchased both of the Witcher games a few days ago when they were 66%. I downloaded patch 1.5, but I can't seem to apply it. Does the GoG.com download of the game include patch 1.5, or if not how do I install it properly?

GOG version includes all patches, except those applied to version modified for Wine on Mac. Unfortunately that patch is not available for GOG version. But all the rest should be included and there is no need to apply any patches.