The short answer is ... it depends. And the longer answer is that it depends on what the starting gravity was and the tolerance for alcohol of the yeast you used. Most wine yeasts can handle 14% ABV without blinking and if your starting gravity was at a normal range for wine making (about 1.090 or potentially about 12% ABV ) then there is really no fear of killing your yeast.
Not sure what 2 cups of sugar weighs (weights are much better than volumes when it comes to wine making) or what volume of wine you were adding those 2 cups to so I cannot say how much you raised the gravity (and so the ABV). You added more berries - so that would increase both the liquid volume (diluting the ABV a touch) and the sugar (raising it a little) but again, since you don't provide enough information it is difficult to say with certainty what the total amount of sugar in your wine is and so what the final potential ABV might be... but there is a near universal law - when you want to kill the yeast through alcohol poisoning you will find that you have the most alcohol tolerant yeast batch on the planet and they just won't croak but when you so hope that your mistake won't kill the yeast you can almost bet the farm that that the yeast you have will give up the ghost sooner than you can say "boo!"
All that said, simply adding K-sorbate is not likely to be very effective. What K-sorbate does is not kill the yeast but it acts as a chemical condom to prevent the yeast from reproducing (budding). What that means is that the present generation of yeast can and will continue to ferment the sugars until they die of old age or of alcohol poisoning.
Despite what folk say on their youtube videos the only really effective way to stop fermentation is to transfer your wine or mead to your fridge and allow the cold temperature to put the yeast into suspended animation, THEN to rack your wine OFF the yeast that will tend to have fallen towards the bottom of your fermenter and THEN to add BOTH K-meta and K-sorbate. In my opinion, since after a week or so - IF you have been pitching a reasonably large enough batch of yeast to happily ferment your juice without any stress you may want to "cold crash" and rack a couple of times (or even more) before you add those two stabilizers in tandem. In other words, the idea is to remove almost every viable yeast cell BEFORE you stabilize the wine. *To try to stop the fermentation in mid flight is pretty much like trying to catch a bullet between your teeth. Penn and Teller can do it ... but they are magicians, if you know what I mean. Mere mortals usually end up in a mess on the floor.
* There are other ways to remove yeast cells that, for example, involve sterile filtering but your wine needs to be very bright and free of any particles to do that successfully otherwise you will simply clog the filters and curse the day you thought you could pull your wine through filters small enough to trap yeast cells too small to see unaided with the human eye.
