Dude, u must get vault coins if u want buy them, u cant get free item from shop if they cost u golden coins of nutaku.
Just play with multiplier slider and u will get all of them "easily" not everything is free.
If u using MOD APK, please dont contact dev official support, u arent helping the modder at all. If u dont like the mod, just dont download and install it.
Turn off 'free cost', and wait for boxes opened. If u set at 100, u get 100 boxes, thats why u stuck there.
I think if u claimed 2x boxes prize, u will get 200x boxes.