You will have to place a copy of any custom waypoint symbols you want displayed on the Montana in the Garmin\CustomSymbols\ directory, as outlined here.
Creating a custom waypoint symbol JUST for placed caches is considerably more tricky, as there is no 'Placed Geocache' waypoint type. They would have to be exported as POI's using a custom POI symbol.
The unfound caches in your database should be displayed with corresponding POI symbols around them with your current settings. As requested, please clear the Garmin\POI\ and Garmin\POI_Stash\ directories and run the macro again.
