No, the search box function has to show all locations, not just a few. You can't edit the number of locations to be displayed on this search box.
Before uploading an icon map to the Map Maker Icon, make sure it is the proper size. In fact, 32x32 and 16x16 versions of an icon map are the common sizes.
To activate billing, go to https://console.cloud.google.com/project/_/billing/enable
Learn more at https://developers.google.com/maps/gmp-get-started