I looked over your telescope details, and they look fine. No red flags. The calculation of the faintest star you can see with that scope is pretty straight forward. Given the light pollution for your location, the faintest star you should be able to detect is magnitude 14.7. Darker locations will allow you to go fainter.
Pluto has a more elliptical orbit that most, taking it from within the orbit of Neptune to farther out. It has been moving farther away from the sun for decades now. When I saw it in a six-inch that was way back in the early 2000's and it was magnitude 13.8 at the time. Now it is magnitude 14.4.
If you look at the Nightbar graphic at the top with Pluto selected, the red dashed line tells the altitude of Pluto throughout the night. The green horizontal line is the 2 airmass line, which is the altitude at which you are looking through twice as much air as overhead. Pluto only just approaches this line. As you move closer to the horizon, the amount of atmospheric extinction increases rapidly. At 2 airmass, the extinction makes Pluto appear to be fainter than magnitude 14.7, taking it just beyond the detection limit in your telescope under these conditions.
Basically, what SkyTools is telling you is that, given the information you have provided, it doesn't think you can spot Pluto, and I don't see anything wrong with that prediction.
Now, you may be just able to detect Pluto after all, but you will need very good conditions and an expert eye. My guess is that if you lower the humidity in SkyTools, change the seeing to excellent, and change your experience level to Expert, it will show up in the list a challenging. The impact of the experience factor was determined empirically, but presumably an expert observer takes precautions to protect their dark adaption and is experienced at using averted vision in the eyepiece, which improves their chances of detecting an object near the limit.
Another way to improve your chances of detection is to switch SkyTools to a darker location.
So, here is how to look at it: you should give Pluto a try, but consider it a challenge. Wait for a night of excellent seeing (especially because it is so close to the horizon) with low humidity, and take steps such as wearing an eye patch over your observing eye to protect your dark adaption. Either that, or go farther away from the lights of the city.
