If you have the space I would split it adding more juice and yeast. You might want to consider some sort of yeast energizer at this point, that way, your yeast will not be too stressed and will minimize the possibility of "off" flavors. I make a lot of applejack and I never add "sugar", I use frozen juice concentrate. It is a bit more expensive method to use, but I believe the flavor is improved. EC-1118 is a monster yeast and ferments very quickly. I personally prefer Red Star Pasteur Red wine yeast, over any other yeast I have tried. It also has an 18% alcohol tolerance and ferments a bit slower, and to me strips out less apple flavor while fermenting. I have used with great success, bakers yeast boiled in water before adding to my fermenter. I did two side-by-side tester batches, and the boiled bakers yeast batch started a little sooner and finished a little sooner as well.