how to set NSButton image and title distance
That's more of an Objective-C question, but I have a working example in one of my plugins...
Sounds like you want a custom NSButton. I don't think there is anything out of the box that lets you specify spacing like that. The NSImageView is placed either leading or trialing to the whole button not relative to the button title.
You could maybe do something like this:
You make the Image position leading but then right align the text and eyeball/manually measure the distance. If you want more control over spacing and padding, etc you will want to use your own button class.