from top to sadist. 3 levels ?

I'm trying to understand levels of dominance and sadism and the words that get used. Please help

Level 1:
I maintain that I don't want to hurt my wife. But I do want to give her pleasure. There is definitely good pain and bad pain. On her the tweezer style nipple clamps are good pain. Clover clamps would be bad pain. I want to deliver good pain (at least for now. We will see where this path leads). I think that makes me a "service top". (At least for now) And the word "sadist" would not be used.

From what I read in another thread, one of the submissive/masochists here in the forum would not be interested in a top who is interested in giving pleasure. (This masochist I guess wants true pain and I suppose true suffering to please her dom). And that leads me to ask about "sadism", possibly many levels of sadism.

Level 3: true sadism or "evil" sadism
The true sadist gets pleasure from the true suffering of others. This level gets pleasure when the pain or humiliation goes beyond consent. That seems simple enough.

Level 2: BDSM sadism or sexual sadism
Here is where I am having difficulty understanding. (Appearance that I actually know what I am talking about may be purely coincidental). The BDSM sadist gets pleasure by pushing his sub into real pain or real humiliation. The masochist sub experiences actual suffering under the hand of the DBMS sadist but she enjoys the suffering for Him. The BDSM gets pleasure from the actual suffering of the sub but has the self-discipline to not go beyond the level of consent.
I have read that BDSM happens when things go past what the sub would ask for but not beyond what the sub can stand.

What I have called level 3 is abuse
Level 1 is pleasure
Level 2: do I have it right?