Man, you should check bones orientation, root , legs and foot. I had this with the DAZ character G8. After you review the orientation (shall be similar as on the Epic skeleton), than adjust the root bone of your model. Remember the rotation values you add to your root bone and simply subscribe this from all child bones. There is an option to project on child bones but not working for me. So, this is a boring manual process, but if you want an IK (with foot rotation), you have to do it. Use skeleton editor tool, and yes, if you have any animation already they all will be all distorted.