Quote- "I was trying to find a good medical definition for psychological addictions, but couldn't find anything consistent. It's even harder finding anything from established medical sites."

Yeah there's a reason for that and it's really really obvious.

As far as what I call the strong almost single-minded desire to spend lots and lots of time perfecting your craft.
We used to call it dedication.
Of course you can't make any money on a diagnosis of dedication.