I never said that the system won’t match players with a difference of more than 677 points. Only that if it did the higher rated player would get 0 points for a win and lose 25 for a loss. I think that in practice this situation is quite rare, or it's possible it was programmed not to occur, I’m not sure. Perhaps a top player can comment if this situation has ever happened to him/her.
The use of the number 400 is arbitrary. So is the starting point of 100 that this site uses. If these numbers were different then players on the leader board would have a different rating, but their ranking would still be in the exact same order! So the choice of these numbers does not affect ranking among players. I suppose 400 is a good choice because it provides a nice spread in the ratings, with few big gaps in between players, but also not too many bunches of players with the same rating.
You now should be able to compute on your own your probability of defeating SATAN-NL. Just use the “P” formula from my last reply. Also, as I said before, you cannot increase your rating simply by playing more games. To close the gap on SATAN-NL you’ll need to find a way to improve your play.