4- electric mat placed
5- level over with modified thinset (let dry)
6- apply modified thinset with v-notched trowel, place ditra (let dry)
7- apply/fill ditra with unmodified thinset, then apply more with notched trowel for setting of tile.
Did I miss something or do something wrong?
Also, why is it recommended that unmodified go between ditra and tile?
You are installing Ditra over another cementitious product. Generally the guidelines call for Unmodified under Ditra when going over a cementitious substrate. Modified should be for setting it to wood only.