Something very important to consider is that your daughter is coming to the age where she should get some input into what she prefers. While ultimately you and your ex-husband are legally entitled to draw up a parenting plan, I would highly caution against disregarding your daughter's preferences. If she wishes to primarily live with her grandma/father, I would at least seriously consider giving her that option.

Also OP you seem to put a lot of the blame on your daughter's reluctance to live with you on her grandma. However, while parental alienation is a possibility, I also think you need to consider that your daughter may have come to similar conclusions on her own. You say that you left your husband because the situation was abusive. You know this and to you it seems completely reasonable. But from your daughter's more limited vantage point it is possible that she blames you for breaking up the family and now sees you as forcing her to move against her will to live with a strange man and his children with whom she doesn't feel comfortable.

It is not an easy situation, however, hard as it may be, i think stepping back and giving your daughter more agency may be the best long term strategy even if it seems painful in the short run. Forcing her to live with you and your BF if she feels very strongly against it, could cause a lot of resentment that might be very hard to reverse. As long as you think she is safe and well-taken care of by her dad/grandma, then I would suggest considering revisiting the shared parenting plan with your daughter's input. Perhaps she could continue primarily living with grandma in the beginning to ease into the transition with frequent visitation to your/your bf's place and then you can reassess the situation on a yearly basis or something.