Do either of you have any idea what your starting SG's were? If they were around typical for balanced juice buckets, you probably have 12-14%ABV already, you are going to have to work really hard to get another yeast started at those kind of levels. You can try, building a yeast starter. As in, hydrate your yeast, add some goferm, let it really get to going good, add about the same amount of must (about 50-100 ml), wait 30 minutes or more, if it keeps bubbling and building now double the volume of liquid you have, repeat until you have almost half of your fermented juic in with the yeast.
My gut tells me you are fighting a big battle, but it could work out. Good Luck!!