Do you think Johnny was going to actually kill... (spoilers).

... the stepfather?

or was he just gonna play him until he got the money he needed? I never could quite figure this out.

Cherry made it seem like he legit gonna do it the way she was warning him at that diner - how Johnny would always use that as leverage over him to get money whenever he wanted, etc.

but the actual impression I got, was that Johnny was NOT a cold-blooded killer. He was just a scammer of the highest degree, who would only kill if he absolutely had to.