My experience is that you can't really trust simulators any of them. I think they may be fairly accurate with clean thin files, but when you have charge offs or other baddies, they don't come close. With that being said paid always looks better than not and if it's updating each month its holding your score back and getting it to stop reporting allows them to recover. If its not updating then paying it will cause an update and could reduce your scores short term, but over time paid will result in a higher score.
It is estimating if everything stays the same and you took that action that is what you could expect. If you add things take things off etc of course it won't be as accurate, BUT it's doable ...what I would do is see where it jumps you after paying it off...it's always a good idea to pay off debts regardless if you decide to leave it on or not but if it doesn't reach you near there or close to there see about getting it removed AFTER it's paid. Just be careful on that part as if it is your oldest account and it is removed it can possibly drop your score since it will affect your Age of accounts. 
The best score simulators are the members on the forums here. More accurate than those gum ball machine sliders. Ask anytime!
