It looks really nice - I especially like that you fussy cut a motif to cover the button.
Getting a button really tight needs quite a bit of brute force! Did your instructions tell you to thread twine through the button loop, then both ends of the twine into the eye of the lethal weopon (long needle) get it through the whole lot, remove the weopon and then tie two half hitches, using one end of the twine over the other end, pull it really tight and then tie a reef knot (or two) to hold it tight, cut the ends of the twine to about an inch and hide the remaining bit under the button?