Still can't get the first letter of 35d, but I will continue to ponder.
I've now identified 6 possible thematic objects (2 going backwards) totaling 26 cells. But i feel like just highlighting a load of 'M's in no way illustrates direct compliance with the instruction so I feel like I must be missing something.
I also assume 13a isn't relevant as the way I read that clue the answer has to be the Js, not the Ms.
Would be good if someone could confirm 13a answer is the Js and that there is no point me just looking for another M as the endgame requires something more complicated than that.
Thanks