Can I use Preview to make this GIF file size smaller?
Yes you can. Open the gif in Preview and you'll get (I got) 48 images. Click on the "View" menu and select "Thumbnails" to display all images as Thumbnails. Give it a second or 2 to display all images. Once that is done go to "Edit" menu and select "display all" or click ⌘-a (command-a) to select all the thumbnails. Next go to "Tools" in the menu bar and select "Adjust Size".  This brings up a pane where you can adjust the image size using standard sizes or by the number of pixels. It will use your settings on all selected thumbnails.