the rest of us are probably make it too complicated by bringing physics into it...
you're maybe making it too complicated by focusing just on the sprite object...
first, re content sizes (there are like a dozen recent threads on the topic): just pick one, how about 320x480? and make your sprite "look right" on that content size. yes, you'll get some letterbox bars added, or zoomEven cropping at runtime on various devices, but typically you're close enough. at least now you know what your "@1x" resolution ought to be.
if you REALLY need to fine-tune it further than that, here are some ideas:
* scale the sprite directly (already covered above, want a 500px wide sprite to be 200px wide? sprite.xScale = 200/500, etc)
* put your sprite in a group, scale the group (same math as above)
* put your entire game in a group, scale THAT group (same math as above)
(suggestion: don't mess with the scene.view's scale, make another group just for this)
* are all your sprite frames on a sheet? if so, mess with sheetContentWidth/Height at runtime before loading (same math as above)
(say you have a 512x512 sheet - if you tell it sheetContentWidth/Height = 256, then your sprite will be half-size, get it? this is typically used for "retina" image support, but you scale it arbitrarily if you wish)